Global tensions are rising following the United States’ missile attack on a Syrian airbase last week. President Trump said Thursday’s attack on the Shayrat air base, which came without U.S. congressional approval, was a response to a chemical weapons attack the Syrian government allegedly launched from the base last week. This attack in Khan Sheikhoun killed 86 civilians, including dozens of children.

International allies of the Syrian government, including Russia, Iran and Hezbollah, have vowed to retaliate against any future attacks against the Syrian regime. On Sunday, the group issued a joint statement saying, “The aggression against Syria oversteps all red lines. We will react firmly to any aggression against Syria and to any infringement of red lines, whoever carries them out.” Over the weekend, Russia also sent a warship armed with cruise missiles to the coast of Syria in response to the U.S. attack.

Meanwhile, U.S. Ambassador to the U.N. Nikki Haley now says President Bashar al-Assad’s ouster is inevitable.

Nikki Haley: “So there’s multiple priorities. It’s—getting Assad out is not the only priority. And so what we’re trying to do is, obviously, defeat ISIS. Secondly, we don’t see a peaceful Syria with Assad in there. Thirdly, get the Iranian influence out. And then, finally, move towards a political solution, because at the end of the day this is a complicated situation. There are no easy answers, and a political solution is going to have to happen. But we know that it is not going to be—there is not any sort of option where a political solution is going to happen with Assad at the head of the regime. It just—if you look at his actions, if you look at the situation, it’s going to be hard to see a government that’s peaceful and stable with Assad.”

U.S. Secretary of State Rex Tillerson is heading to Russia on Tuesday. Ahead of the meeting, Tillerson accused Russia of being partially responsible for the chemical weapons attack, saying, “Either Russia has been complicit or Russia has been simply incompetent.” In Russia, meanwhile, lawmaker Mikhail Yemelyanov has accused the United States of provoking a nuclear war.

Mikhail Yemelyanov: “This act goes far beyond just Syria, because clearly Russia supports the legal Syrian government and takes part to a certain scale in this conflict. Therefore, such strikes are an act not just against Syria, but also against Russia. Moreover, when Americans were striking the airport, they didn’t know if our citizens were there or not. So this situation may lead at least to a repetition of the Cuban missile crisis, which almost pushed the world onto the edge of a nuclear war.”

The U.S. attack on the air base appears to have caused little damage to the Syrian regime’s military capabilities. The government was able to largely evacuate the Shayrat air base before the attack, since the U.S. had warned Russia before the missile strikes. On Friday, only hours after the attack, the base was once again operational, and the Syrian military resumed flights. On Saturday, activists say at least one civilian was killed in airstrikes on a residential neighborhood of Khan Sheikhoun—the same town where the chemical weapons attack occurred on Tuesday. Majed Khattab, a resident of the town, told The Washington Post, “The American strikes did nothing for us. They can still commit massacres at any time.”