WASHINGTON (AP) - A U.S.-Russia civilian nuclear power deal signed Tuesday ran into immediate trouble on Capitol Hill, where two senators said they would try to block the deal because it could hurt efforts to prevent Iran from getting nuclear weapons.

Sen. Norm Coleman, R-Minn., along with Sen. Evan Bayh, D-Ind., are circulating a letter that will urge President Bush not to send the pact to Congress.

Under the deal signed Tuesday by U.S. and Russian officials in Moscow, the United States would get access to Russian state-of-the art nuclear technology. The pact would help Russia establish an international nuclear fuel storage facility by importing and storing spent fuel. The U.S. controls the vast majority of the world's nuclear fuel.

"I am very disappointed by the administration's insistence on moving forward to sign a nuclear cooperation arrangement with the Russians," Coleman said in a telephone interview. "Particularly at a time when Russia's actively undermining our foreign policy on various fronts, most importantly with respect to Iran."

In a statement, Bayh added: "U.S.-Russian nuclear cooperation is important, but stopping Iran from gaining the capacity to make nuclear weapons is an even higher priority. Russia is not doing all it can to curb Tehran's nuclear ambitions, and we need to use all tools at our disposal to get more cooperation from Moscow."

Coleman and Bayh say Russia's exports of nuclear fuel to Iran's Bushehr nuclear power plant and opposition to United Nations sanctions against Iran make the new deal suspect. In the letter, provided to The Associated Press, the senators say the deal "would pave the way for the increased commercialization of Russia's nuclear energy sector and could be construed as U.S. approval of its proliferation activities in Iran."

But the Bush administration now views Russia as a partner in the effort to persuade Iran to abandon nuclear weapons ambitions. A State Department official said the U.S. did not view Russia's assistance to Iran's Bushehr nuclear power plant as a reason to not sign the new deal.

"In fact, the president has made clear his support for Russia's supply of nuclear fuel to Bushehr because it demonstrates that Iran does not need to possess the complete nuclear fuel cycle with its proliferation risks to take advantage of the peaceful uses of nuclear energy," said the official, who asked not to be identified because he wasn't authorized to speak on the record.

To get the deal in place, Bush must send it to Congress. It would become effective unless Congress passes legislation within 90 days to block it.

A bill pending in the Senate would block a U.S.-Russia nuclear deal unless Russia has stopped cooperating with Iran's nuclear or advanced conventional and missile program, or Iran has stopped enriching uranium. That legislation, sponsored by Oregon Republican Gordon Smith, has 70 co-sponsors, but Coleman said it's no sure bet that it would be passed in time to block the deal.

"Even if you have the votes, it doesn't mean you'll have time to take it up and debate it," he said. "There's no guarantee that leadership will schedule a vote." He called passage "a high bar."

"There is a great deal of concern on the part of many members of Congress," Coleman added. "I disagree with the president, I think it's bad policy."

He said that Bush could use congressional opposition as leverage in extracting conditions from the Russians for the deal - "at a minimum, they have to stop with any advanced conventional weapon assistance to the Iranians."