CHICAGO (CBS) — It’s been one of the biggest national stories of the week, but Gov. Bruce Rauner on Friday said he’s “not familiar” with a letter 47 Republican U.S. senators sent to the leaders of Iran, amid the Obama administration’s efforts to negotiate a nuclear deal.

Moments after Rauner had said U.S. Sen. Mark Kirk has been a phenomenal senator for Illinois, and that he’s pulling for Kirk to win another term in 2016, the governor was asked if he thought Kirk signing the letter to Iran’s ayatollah would hurt his re-election chances.

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Rauner pleaded ignorance.

“I’m sorry, I’m not familiar with the letter,” he said.

When WBBM pointed out people likely would be surprised to hear the governor is not familiar with a story that has dominated national news headlines all week, Rauner insisted he’s more focused on Illinois’ problems.

“You know what? I’m very focused, and federal issues are not my issue,” he said.

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U.S. Sen. Dick Durbin has said the letter undermines the Obama administration’s efforts to negotiate a deal with Iran to halt any development of a nuclear weapon. He called it “a new low” in the ongoing division between Republicans and Democrats in Congress.

“It’s virtually unprecedented,” Durbin said. “Here we are in the middle of delicate negotiations. We’re down to the last few days. We’re trying to reach a point with our allies where Iran is going to stop any development of a nuclear weapon, to put inspectors on the ground, and 47 Republican senators elbowed their way into the room and say ‘Don’t waste your time. We get the last word on this, and we’re not going for it.’ It really is irresponsible, as far as I’m concerned.”

The letter, written by freshman Sen. Tom Cotton, was addressed to the “Leaders of the Islamic Republic of Iran” and presents itself as a constitutional primer to the government of an American adversary. Senate Majority Leader Mitch McConnell of Kentucky’s signature is on it, as are those of several prospective presidential candidates.

Kirk also defended the letter.

“In exchange for allowing Iran to maintain the capabilities to build nuclear weapons, the Administration promises to ‘comprehensively lift’ as many as 14 Iran sanctions laws, many of which passed with bipartisan veto-proof majorities. There is no Constitutional authority granting a president unilateral power to repeal American law. Sanctions should not be weakened until Iran stops its nuclear weapons program, stops supporting and exporting terrorism, stops aggression against its neighbors, stops egregious human rights abuses, and stops threatening to annihilate Israel. A better deal, with bipartisan congressional backing, is the best insurance policy against a nuclear Iran, a destructive arms race, and war in the Middle East,” Kirk said in a statement earlier this week.

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Rauner was planning to take part in a fundraiser for Kirk next week.