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The steps taken at the nuclear safety summit in Washington D.C. will make the world a safer place, U.S. President Barack Obama said Tuesday.

"Today’s progress was possible because these leaders came not simply to talk but to take action, not simply to make pledges of future action but to commit to meaningful steps that they are prepared to implement right now," Obama said as he wrapped up the two-day conference.

Obama said the participants all agreed to the seriousness of the threat of nuclear attacks, a change from the beginning of the summit when there was a range of views on the issue.

"Today we are declaring that nuclear terrorism is one of the most challenging threats to international security," Obama said.

He said all nations also endorsed the goal to secure all vulnerable nuclear materials around the world in four years time.

Obama said some important achievements were reached during the summit. Canada said it would return its stockpile of enriched uranium to the United States, while Ukraine announced it will give up its entire stockpile of weapons-grade uranium by 2012 — most of it this year.

He said Chile and Mexico also announced they would give up their entire stockpile of enriched uranium, and that nations such as Argentina and Pakistan had announced steps to strengthen port security and prevent nuclear smuggling.

Co-operation questioned

Obama was asked by a reporter how countries that have been at odds over different issues will co-operate since everything to be done is on a voluntary basis without any binding commitment.

"The point is that we've got world leaders who have just announced that, in fact, this is a commitment that they're making. I believe they take their commitments very seriously," Obama said. "If what you're asking is, do we have a international one-world law-enforcement mechanism, we don't. We never have."

Shortly after the opening of the conference, Canada, the United States and Mexico announced a plan to convert Mexico's research reactor to low-enriched uranium from highly enriched uranium. About 11 kilograms of highly enriched uranium will be shipped from the Mexican reactor to the U.S.

Canada will contribute about $5 million to the conversion project.

Obama also announced that the U.S. is joining with Canada in calling on nations to commit $10 billion to extend a global partnership that would strengthen nuclear security around the world.

Prime Minister Stephen Harper, who was among 47 world leaders gathered at the meeting said that Canada has not made that request, but there have been discussions among G8 partners about the initiative.

"Canada is not the originator of the request but obviously we're going to be looking at this request very seriously and I know all our G8 partners will do the same," Harper said.

China may join Iran sanctions

The G8 signed on to the program at its 2002 summit in Kananaskis, Alta. Since then, the group has spent more than $600 million helping other countries decommission and secure their nuclear material.

Obama also said he is confident China will join other nations in pressing for tough new sanctions on Iran for continuing to seek nuclear weapons in defiance of the international community.

"Words have to mean something," Obama said. "There have to be some consequences."

Hu and Obama met for 90 minutes on Monday after which U.S. officials said the two agreed to tell their aides to work on a tough new sanctions program. However, a Chinese spokesman did not mention sanctions in his description of the meeting.