China agreed to work with the United States on a possible sanctions regime against Iran and Ukraine announced it would give up its weapons-grade enriched uranium as a US-hosted nuclear summit got under way on Monday evening. President Barack Obama opened the global security summit in Washington after two days of meetings with presidents and prime ministers of the 47 countries assembled to recharge efforts to keep nuclear material out of terrorist hands. China’s incremental move towards US ambitions to sanction Iran and Ukraine’s plans get rid of highly-enriched uranium put some wind in Mr Obama’s sails as he presses world leaders to join him in locking down all nuclear materials within four years. His meeting with Chinese president Hu Jintao was the last of the summit warm-up sessions before the US leader sat down with his guests at a working dinner. After the Hu meeting, White House national security aide Jeff Bader said Iran was a major topic of discussion at the 90-minute session. “They’re prepared to work with us,” Mr Bader said, interpreting that willingness as “another sign of international unity on this issue”. The upbeat assessment reflected a recent warming of US-Chinese diplomatic ties, but the meeting produced no breakthroughs. Chinese spokesman Ma Zhaoxu did not mention sanctions in a statement on Mr Hu’s meeting with Mr Obama. Mr Ma said China hoped all parties would step up diplomatic efforts and seek ways to resolve the Iranian nuclear issue through negotiations. “China and the US share the same overall goal on the Iranian nuclear issue,” the Chinese statement said.