The Obama administration on Monday assailed Republican lawmakers who signed an open letter to Iranian leaders for attempting to undermine ongoing negotiations aimed at curbing Tehran's nuclear program. "I think it's somewhat ironic that some members of Congress want to make common cause with the hardliners in Iran," Obama said. "It's an unusual coalition." Drafted by freshman Sen. Tom Cotton (R-Ark.), the letter warned that Congress or a future president could nullify any nuclear agreement reached between the White House and Iran.

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