WASHINGTON President Barack Obama's drive for tougher sanctions on Iran picked up momentum on Monday in talks with Chinese President Hu Jintao that also focused on their countries' fractious economic relationship.
Their 90-minute encounter came at the start of a two-day nuclear security summit of nearly 50 countries aimed at finding ways to prevent terrorists from getting their hands on weapons-grade nuclear material.
Ukraine provided the first example by agreeing to give up its highly enriched uranium.
Iran's nuclear program, which the West fears is a cover to build an atomic bomb, is not on the agenda of the summit, but the presence of so many world leaders in one place gave Obama an opportunity to again make his case for fresh sanctions to be imposed on Tehran over its refusal to halt uranium enrichment.
U.S. and Chinese officials who briefed reporters after the talks described a positive, constructive atmosphere on Iran. China, which has close economic ties with Iran, has been reluctant to sign on to tougher sanctions.
Obama also raised U.S. concerns about China's currency, the yuan, and urged the country to move to a more market-oriented exchange rate.
Washington has been pressing Beijing to lift the value of the yuan, and many U.S. lawmakers say that by deliberately holding down its currency China is giving its firms an unfair export subsidy that costs jobs in many countries.
U.S. Treasury Secretary Timothy Geithner and White House economic adviser Larry Summers attended the meeting between Obama and Hu. A U.S. official said Obama had also raised the issue of market access for U.S. goods.
On Iran, Hu told Obama that China and the United States shared the same overall goal, Chinese Foreign Ministry spokesman Ma Zhaoxu said.
Ma's comments confirmed China's recent decision to join in discussions on reining in Iran's nuclear program but did not indicate a new willingness to embrace harsher sanctions, such as ones that would target the Islamic Republic's energy sector.
Ma also repeated China's standard call for "dialogue and negotiations" with Iran.
A U.S. official said China and the United States agreed their representatives would work on a sanctions resolution.
Hu's agreement to attend the summit was perceived as a positive sign in Washington after U.S.-Chinese relations were strained by Obama's meeting with the Dalai Lama, China's Internet censorship, and U.S. pressure over China's currency.
IRAN DISMISSES SUMMIT
Iran dismissed the U.S. summit and said it would not be swayed by any decisions made there. "World summits being organized these days are intended to humiliate human beings," Iranian President Mahmoud Ahmadinejad said in Tehran.
Obama also had a one-on-one meeting with Jordan's King Abdullah, who like many Arab leaders is worried about Iran's potential for Iran developing a nuclear weapon and triggering a Middle East arms race.
The summit in Washington's downtown convention center, which was surrounded by a heavy security cordon of troops and police and high fences, is the culmination of a hectic period of nuclear diplomacy for Obama.
Last week he signed a new treaty to cut U.S. and Russian nuclear arsenals and unilaterally announced the United States would limit its use of nuclear weapons, a plan that came under heavy fire from his conservative critics.
The summit -- the biggest U.S.-hosted assembly of world leaders in six decades -- will be a test of Obama's ability to rally global action on his nuclear agenda.
It had its first tangible outcome when Ukraine announced it would give up its stockpile of highly enriched uranium by 2012, most of it this year.
Kiev has enough nuclear material for several weapons. It will convert its civil nuclear program to operate on low-enriched uranium. Washington agreed to provide technical and financial support for the effort, U.S. officials said.
Canadian Prime Minister Stephen Harper, who is also attending the summit, pledged to send a "significant quantity" of Canada's spent nuclear fuel to the United States by 2018.
A draft final communique shows leaders will pledge to work toward safeguarding all "vulnerable nuclear material" within four years and take steps to crack down on nuclear smuggling.
The list of leaders in attendance ranged from heads of state of traditional nuclear powers like Russia and France to nuclear-armed foes like India and neighboring Pakistan.
(Writing by Steve Holland and Ross Colvin; Editing by David Storey)