Corker is working on legislation that would force the Obama Administration to submit any deal reached with Iran for a vote by Congress. The White House earlier threatened to veto such a measure.
White House Chief of Staff Denis McDonough, in the three page letter released publicly Saturday evening, told Corker his legislation could be detrimental to the talks with Iran by "emboldening Iranian hard-liners, inviting a counter-productive response from the Iranian majiles (Majles, the Parliament); differentiating the U.S. position from our allies in the negotiations; and once again calling into question our ability to negotiate this deal."
As the U.S. and Iran prepare for the next round of negotiations this coming week, there has been a growing debate between Republicans on Capitol Hill and the Obama Administration about how much authority Congress has regarding the fate of the agreement.
"The legislation you have introduced in the Senate goes well beyond ensuring that Congress has a role to play in any deal with Iran. Instead, the legislation would potentially prevent any deal from succeeding by suggesting that Congress must vote to 'approve' any deal and by removing existing sanctions waiver authorities that have already been granted to the President," McDonough wrote.
The chief of staff said that only Congress can terminate the existing Iran sanctions that are included in laws, but the President can relax some sanctions put into place by executive order unilaterally.
One of the major issues between the U.S. and Iran is the timetable for lifting of the sanctions.
"If congressional action is perceived as preventing us from reaching a deal, it will create divisions within the international community, putting at risk the very international cooperation that has been essential to our ability to pressure Iran. Put simply, it would potentially make it impossible to secure international cooperation for additional sanctions, while putting at risk the existing multilateral sanctions" now in place, McDonough said in his letter.
For his part, Corker on Sunday released a statement: "On this issue where Congress has played such a vital role, I believe it is very important that Congress appropriately weigh in before any final agreement is implemented."
Corker also urged the President not to go to the United Nations for a vote regarding lifting of the sanctions on Iran, as Reuters reported was being considered.
"Enabling the United Nations to consider an agreement or portions of it, while simultaneously threatening to veto legislation that would enable Congress to do the same, is a direct affront to the American people and seeks to undermine Congress' appropriate role," he wrote.
The chief of staff told Corker, "The Administration's request to the Congress is simple: let us complete the negotiations before the Congress acts on legislation" and added "we will aggressively seek public and congressional support for a deal -- if we reach one -- because we believe a good deal is far better than the alternatives available to the United States."
McDonough also mentioned a separate letter sent to Iran's leadership and signed by 47 Republican senators. Corker did not sign it.
The letter maintained that a future president could reverse some of what is agreed to in these ongoing negotiations and said any agreement reached would need congressional approval.
It has generated much controversy
. It also drew rebuttal from Iran's foreign minister, who called it a propaganda ploy.
On Sunday, Iran's speaker of parliament and former nuclear negotiator, Ali Larijani, said the letter signed by the senators tarnished Washington's reputation internationally, according to state-run Tasnim news agency. He said it showed that the United States is untrustworthy, and he advised current negotiators to be wary.
McDonough also said the letter's premise was incorrect.
"Non-binding agreements -- like the deal we are negotiating with Iran...are an essential element of international diplomacy and do not require congressional approval," McDonough said.
Secretary of State John Kerry, who heads back to Switzerland on Sunday for more talks with Iranian representatives, again blasted that letter from the 47 Republicans.
"It is a direct interference with negotiations in the executive department," he said at a news conference in Egypt. "It is completely without precedent, and it is almost inevitable it will raise questions in the minds of the folks with whom we are negotiating."