After years of negotiations, the United States and Ukraine agreed to a nuclear cooperation deal that will prevent a Ukrainian company from providig a key component to a nuclear reactor Russia is building in Iran. The United States is urging Russia to halt its nuclear energy assistance to Iran, which Washington says is trying to produce nuclear weapons under the cover of a civilian energy program. Russia says the contract to complete a 1,000 megawatt nuclear reactor in Bushehr on the Gulf coast is legal and safe, since Iran is a member of the International Atomic Energy Agency and is subject to its inspections.