A Republican US senator says he will try to block a civil nuclear pact if President George W. Bush sends it to Congress. Sen. Norm Coleman says the deal could undermine efforts to prevent nuclear proliferation in Iran. Coleman and Democratic Sen. Evan Bayh are circulating a letter that will urge Bush not to send the pact to Congress. Under the deal, signed Tuesday, the United States would get access to Russian state-of-the art nuclear technology. The deal would help Russia establish an international nuclear fuel storage facility by importing and storing spent fuel.