Sen. Tom Cotton, R-Ark., is treading carefully in his criticism of President Donald Trump’s memorandum of understanding with Iran, a far cry from his reaction to a remarkably similar deal former President Barack Obama penned with Tehran in 2015, reports Politico.

Cotton, the chair of the Senate Intelligence Committee and the No. 3 Senate Republican, on Thursday said he has “concerns that certain aspects of this deal are stepping in the wrong direction.”

“[Trump] deserves enormous credit for making Iran weaker than it's been in decades, and we need to make sure that we don't squander the leverage that we built across six years,” he told Fox News.

Eleven years ago, Cotton took a different tone, joining 46 Republican senators in writing a letter addressed to leaders of the Islamic Republic of Iran declaring that any agreement made with the Obama administration without legislative approval could be reversed by the next president “with the stroke of a pen.”

Other Republican senators have expressed concerns about the current deal, including Ted Cruz of Texas, Roger Wicker of Mississippi, Bill Cassidy of Louisiana, and John Cornyn of Texas.

“Since Day 1, I have supported President Trump's efforts to end Iran's 47-year threat to the United States and our partners. I am concerned that the memorandum of understanding negotiates away the victories of Operation Epic Fury in ways that are completely out of step with the President's goals,” Wicker said in a statement Thursday.

“The terms of the MOU that have been released start off with tens of billions of dollars immediately being released to Iran before it makes a single nuclear concession. I think that's a mistake,” he said.

Top U.S. negotiators Jared Kushner and Steve Witkoff were already in Switzerland, working through the technical details of planned negotiations on Iran’s nuclear program.

The interim deal gives negotiators 60 days to reach a nuclear agreement, though that period can be extended.