World leaders continue to meet in Washington today at a summit on nuclear terrorism. It’s the largest international gathering hosted by a US president since the UN’s founding in 1945. On Monday, President Obama pressed for international support to impose new sanctions on Iran for its nuclear activities. Iran wasn’t invited to the meeting and says it will hold its own gathering later this month. Meanwhile, Ukraine announced it will dispose of its stock of highly enriched uranium, a key component of nuclear weapons. The summit comes ahead of a new round talks next month on strengthening the Non-Proliferation Treaty. At the United Nations, Secretary-General Ban Ki-moon urged all member states to ratify the NPT.

UN Secretary-General Ban Ki-moon: “All the member states who have not done so should participate in the NPT treaty. That is an obligation of all member states of the United Nations. Likewise, I am also urging — I am going to urge in Washington that all the countries who have not signed and ratified the Comprehensive Nuclear Test Ban Treat, CTBT, should also do so without further delay. That is a part of our common commitment to make this world free of nuclear weapons.”