By Patricia Zengerle
WASHINGTON (Reuters) - Democratic U.S. senators introduced a resolution on Monday opposing more sanctions on Iran unless nuclear talks fail or Tehran breaks an agreement, countering a push for tougher sanctions backed by Republicans that President Barack Obama has pledged to veto.
"For those who agree that the sanctions bill in the Banking Committee is detrimental, this resolution provides an option in support of diplomacy," Democratic Senator Dianne Feinstein, a leading co-sponsor of the resolution with Senator Chris Murphy, said in a statement.
Backing the Obama administration, she said enacting new sanctions during the negotiations would "gravely undermine" efforts to reach a nuclear agreement with Tehran.
The Senate Banking Committee is due to vote later this week on legislation being developed by Republican Senator Mark Kirk and Democrat Robert Menendez that would toughen sanctions on Iran if there is no nuclear agreement before the end of June.
Six world powers - the United States, Britain, China, France, Germany and Russia - have given themselves until the end of June to produce a diplomatic breakthrough with Iran and end a long-running dispute over Tehran's nuclear ambitions.
Obama pledged in his State of the Union address last Tuesday to veto the Kirk-Menendez measure, which has strong support among many Republicans, who contend Obama is so eager to reach an important agreement with Iran that he is giving up too much in the talks.
The dispute contributed to a diplomatic flap. U.S. House of Representatives Speaker John Boehner, a Republican, announced the day after Obama's address that he had invited Israeli Prime Minister Benjamin Netanyahu to address Congress on Iran, without consulting the Obama administration or congressional Democrats.
Netanyahu on Sunday defended his planned speech, saying he had a moral obligation to speak out on an issue that poses a mortal threat to Israel. His visit to Washington next month has drawn accusations in Israel that Netanyahu is undermining the country's core foreign alliance in an effort to win an election two weeks after the trip.
The new resolution's other co-sponsors include Democratic Senators Tom Carper, Dick Durbin, Al Franken, Martin Heinrich, Patrick Leahy, Jeff Merkley, John Tester and Sheldon Whitehouse, as well as Senator Angus King, an independent who caucuses with Democrats.