World leaders gather in The Hague for two days of nuclear security talks starting Monday.

A G7 meeting was also hastily added to the agenda to give leaders a chance to discuss a response to Russia's annexation of Crimea.

Before the summit, U.S. President Barack Obama and Chinese President Xi Jinping pledged cooperation between their countries.

(SOUNDBITE) (English) CHINESE PRESIDENT XI JINPING SAYING:

"I wish to emphasize that China is firmly committed to... building a new model of major country relations. We are committed to our position of no confrontation, no conflict, mutual respect, and win-win cooperation with regard to the United States."

Obama said the U.S.-China relationship was as important as any in the world, and that they could work through their differences.

(SOUNDBITE) (English) UNITED STATES PRESIDENT BARACK OBAMA SAYING:

"We're also able to work through frictions that exist in our relations around issues like human rights, deal