Sen. Tom Cotton, R-Ark., warned Thursday that any effort by President Obama to lift financial sanctions on Iran would be met with a quick congressional response from Republicans, including hearings and legislation.

"I want to be very clear. If the president moves to grant Iran access to the U.S. dollar, whether directly or indirectly, there will be consequences," Cotton said on the Senate floor.

"If there is any statement, guidance, regulation or executive action that opens the U.S. banking sector to Iran, even a crack, the Senate will hold hearings with each official who assured the American people last summer that the Ayatollahs would never access the dollar," he said. "We will explore whether they lied back then, or whether they intend to resign in protest now."

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Cotton's warning comes just a day after the Obama administration said it would be "advising" foreign banks what transactions they can do with Iran without running afoul of U.S. sanctions. That acknowledgement came after reports that the administration may be thinking of giving Iran access to dollar-denominated transactions.

The administration has offered various responses to that claim, but hasn't yet convinced many Republicans that the idea is off the table.

Cotton stressed that senior Obama officials promised Congress that Iran wouldn't have any access to dollar transactions, either directly or indirectly, and said Obama now can't be trusted based on recent reports.

"We should call this for what it is: concession creep," he said. "We can no longer trust the administration to hold fast to the specific concessions contained in the four corners of that deal."