Russia and the United States have tentatively agreed to a weapons inspection program that would allow Russians to visit nuclear sites in America to count missiles and warheads.
 
The plan, which Fox News has learned was agreed to in principle during negotiations, would constitute the most intrusive weapons inspection program the U.S. has ever accepted.
 
Foreign Minister Sergey Lavrov, who met with Secretary of State Hillary Clinton, said publicly Tuesday that the two nations have made "considerable" progress toward reaching agreement on a new strategic arms treaty.
 
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