As many as five Afghan civilians have been killed and another eighteen wounded in a US attack in Afghanistan. Witnesses say US forces opened fire on a passenger bus near the Afghan city of Kandahar earlier today. The bus driver and a passenger told the New York Times a US convoy opened fire just as the bus began pulling over to the side of the road to allow another military convoy to pass. The bus was said to be full of civilian passengers when US troops opened fire. All of the windows on one side of the bus were shot out. Some of the wounded were left in critical condition, and the death toll could rise.

President Obama is hosting scores of world leaders in Washington today for a summit focusing on unsecured nuclear materials. On Sunday, Obama began a series of meetings with visiting delegations from forty-six countries. Ahead of the summit, Secretary of State Hillary Clinton said the aim is to keep nuclear weapons away from terrorist groups.

Secretary of State Hillary Clinton: “The risk of nuclear attack has actually increased. And the potential consequences of mishandling this challenge are deadly. We are trying to make this summit the beginning of sustained international effort to lock down the world’s vulnerable nuclear materials within four years and reduce the possibility that these materials will find their way into the hands of terrorists.”

As the Obama administration pledged nuclear cooperation around the summit, it also took pains to reassert the predominance of the US nuclear arsenal. In an interview with ABC News, Clinton said the US is spending $5 billion this year to “modernize” its nuclear weapons.

Secretary of State Clinton: “We intend to maintain a robust nuclear deterrent. Let no one be mistaken. The United States will defend ourselves and defend our partners and allies. We intend to sustain that nuclear deterrent by modernizing the existing stockpile. In fact, we have $5 billion in this year’s budget going into that very purpose. And with this emphasis on our nuclear stockpile and the stewardship program that we are engaged in, that we’ll be, you know, stronger than anybody in the world, as we always have been, with more nuclear weapons than are needed many times over, and so we do not see this as, in any way, a diminishment of what we’re able to do.”

President Obama is vowing a speedy appointment to replace the retiring Supreme Court Justice John Paul Stevens. The eighty-nine-year-old Stevens announced Friday he’ll step down at the end of the Court’s regular session in June. At the White House, Obama paid tribute to Stevens’ thirty-five years on the bench.

President Obama: “He has worn the judicial robe with honor and humility. He has applied the Constitution and the laws of the land with fidelity and restraint. He will soon turn ninety this month, but he leaves his position at the top of his game. His leadership will be sorely missed…Now, as Justice Stevens expressed to me in the letter announcing his retirement, it is in the best interest of the Supreme Court to have a successor appointed and confirmed before the next term begins, and so I will move quickly to name a nominee, as I did with Justice Sotomayor.”

Stevens has long been regarded as the leader of the “liberal” wing of the Supreme Court. In a statement, the American Civil Liberties Union said, “The civil liberties legacy of Justice Stevens is deep and broad. He has promoted racial equality, supported gay rights and defended a woman’s right to choose…Without his leadership, the Bush administration might well have succeeded in its effort to deprive Guantánamo detainees of any rights and any access to US courts.”

The Obama administration’s choice to head the Justice Department’s Office of Legal Counsel has withdrawn herself from consideration after more than a year of Republican-led opposition to her nomination. The nominee, Dawn Johnsen, is a law professor at Indiana University. Republicans had criticized her for opposition to Bush-era interrogation and surveillance policies, as well as her work for an abortion rights group two decades ago. She was left off a list of fifteen recess appointments by President Obama last month.

The Obama administration is now defending the US military’s indiscriminate killing of twelve Iraqis after refusing to back calls for a probe. Last week, the watchdog website WikiLeaks released a classified US military video showing a US helicopter gunship firing on Iraqi civilians in 2007. On Sunday, Defense Secretary Robert Gates offered a staunch defense of the US servicemembers who carried out the attack. Speaking to ABC News, Gates claimed the forces were operating in a “combat” and “split-second” situation, despite the fact the civilians weren’t engaged in any hostile act and the helicopter had hovered above them for several minutes. Gates made the comments in response to a question of whether the video footage would damage the US image abroad.

Defense Secretary Robert Gates: “They’re in a combat situation. The video doesn’t show the broader picture of the — of the firing that was going on at American troops. It’s obviously a hard thing to see. It’s painful to see, especially when you learn after the fact what was going on. But you — you talked about the fog of war. These people were operating in split-second situations. And, you know, we — we’ve investigated it very thoroughly.”

The rescue effort has ended at West Virginia’s Upper Big Branch Mine after the discovery of the bodies of the four miners who remained missing after last week’s explosion. Their deaths brought the death toll to twenty-nine in the worst US mining disaster in nearly forty years. West Virginia Governor Joe Manchin held a news conference Saturday shortly after the bodies were found.

Gov. Joe Manchin: “We did not receive the miracle we prayed for. We have accounted for four miners that had been unaccounted for. We have a total of twenty-nine brave miners who we are recovering at this time. None of the chambers had been deployed, and none of our miners suffered. So this journey has ended, and now the healing will start.”

In a statement, President Obama called for a probe into the mine blast, saying the tragedy requires “accountability.” The owner and operator of the mine, Massey Energy, has been cited for dozens of safety violations in recent years, with fifty-seven citations just last month.

Poland has declared a week of national mourning following Saturday’s plane crash that killed its president and dozens of top political and military leaders in Russia. President Lech Kaczynski was heading a delegation to Russia to commemorate the 1940 massacre of over 20,000 Poles by the Soviet Union secret police. The ceremony had been seen as a sign of growing reconciliation between Poland and Russia. At least ninety-six people died in the crash. At the Polish embassy in Washington, Polish Ambassador Robert Kupiecki thanked Americans for their condolences.

Polish Ambassador Robert Kupiecki: “I would like to extend my words of thanks, of gratitude, to President Barack Obama and the American people, many people who contacted the embassy, who contacted me personally, sharing their words of sympathy and condolences. Thank you very much for your attention.”

In addition to top government officials, the victims included the former Polish trade unionist Anna Walentynowicz, whose firing in 1980 led to the founding of the Polish trade union Solidarity.

In Thailand, public funerals are being held today for protesters killed in clashes on Saturday in Bangkok. At least seventeen civilians were killed and hundreds more wounded when police fired live ammunition into a crowd of thousands of so-called “Red Shirt” protesters in Bangkok’s old quarter. Four police officers were also killed in the ensuing unrest. It was Thailand’s worst political violence in nearly two decades. The Red Shirts have led a series of protests calling for the Thai parliament to be dissolved.

The Israeli military is enacting a new order this week that could lead to the expulsion or imprisonment of tens of thousands of Palestinians on the occupied West Bank. Under the order, any Palestinian or foreigner in the West Bank without Israeli-issued ID could be deported or jailed for up to seven years. Palestinians from Gaza or foreign-born spouses of Palestinians are expected to be among the first targets if the order is enforced. In a statement, a coalition of ten Israeli human rights groups, including B’Tselem and Rabbis for Human Rights, called for the policy to be revoked, saying, “The orders…are worded so broadly such as theoretically allowing the military to empty the West Bank of almost all its Palestinian inhabitants.”

Kazakhstan has granted the US permission to conduct overflights to move troops and equipment to Afghanistan. The US says the flights will allow for quicker deployments of US troops into the Afghan war zone.

And the Obama administration has confirmed it’s denying climate aid to at least two countries that refused to sign on to last year’s Copenhagen environmental accord. The State Department has canceled funding of $3 million to Bolivia and $2.5 million for Ecuador. Bolivia vocally opposed the accord, while Ecuador has issued its tacit rejection by refusing to sign on so far. A coalition of southern, island and developing countries opposed the non-binding accord largely over its exclusion of mandatory and robust emissions cuts at the levels recognized as necessary to avert devastating climate change. There are fears the funding cuts could signify the Obama administration will attempt to punish nations financially for defying the US stance on climate agreements. In a statement, Kate Horner of Friends of the Earth said, “The US is acting like a bully, strong-arming the most vulnerable countries to get them to sign onto an ineffective and unfair deal that will not move the world closer to a just climate agreement.”