Republican lawmakers are fuming that the Obama administration is asking the U.N. Security Council to endorse the newly struck Iran nuclear deal before Congress gets a chance to have its say. 

A vote on the agreement before the Security Council already has been set for Monday, with the resolution itself written and ready for consideration. Top-ranking lawmakers have fired off a series of letters to the president urging him to delay the vote, calling it an "affront" to the public and Congress to go to the U.N. first. 

"President Obama's attempt to circumvent Congress and hastily move forward with a United Nations Security Council vote on the Iran nuclear agreement is outrageous," Sen. David Perdue, R-Ga., said in a statement. 

Under legislation agreed to earlier this year, Congress has a 60-day window to review the deal, which curbs Iran's nuclear program in exchange for billions of dollars' worth of sanctions relief. 

The White House is lobbying Congress hard, and faces an uphill battle trying to convince members of both parties to support the agreement. 

Congress would have a direct say over the status of U.S. sanctions on Iran, not necessarily the rest of the deal. But Republicans claimed Capitol Hill was being sidelined by the U.N. Security Council plans, considering they probably won't vote until September. 

"The full 60 day review period and parliamentary procedures prescribed by the Iran Nuclear Agreement Review Act should be allowed to play out before action at the Security Council," House Foreign Affairs Committee Chairman Ed Royce, R-Calif., and House Homeland Security Committee Chairman Michael McCaul, R-Texas, wrote in a letter to Obama. "... while we understand that you intend to veto any joint resolution of disapproval that Congress may send to your desk, it would be entirely inappropriate and divisive for your Administration to vote to lift UN-backed sanctions should Congress reject the final agreement and override a presidential veto to that effect." 

The White House says the U.N. Security Council action, though, doesn't have an impact on U.S. sanctions that Congress has jurisdiction over. Further, White House Press Secretary Josh Earnest said Friday the process does "reflect significant deference to the United States Congress," as the U.N. as a whole would not adopt the deal for 90 days. 

"And that means that Congress will have ample opportunity to [consider the agreement] within their 60-day window before this agreement is sort of formally adopted after the U.N. Security Council vote," Earnest said. 

Noting that the deal was struck by the five permanent members of the Security Council, he said it is "natural that those who are party to this agreement would be acting promptly to take it up." 

But Republicans don't even want the Security Council to act. They're also angry that Secretary of State John Kerry said recently that if Congress rejects the deal, the U.S. "would be in noncompliance with this agreement and contrary to all of the other countries of the world." 

Sen. Mark Kirk, R-Ill., said in a statement he was "shocked" by the comment, and called the plan to "preempt" Congress' review with a Security Council vote a "breathtaking assault on American sovereignty and Congressional prerogative. " 

Even if Congress votes down the deal, Obama has vowed to veto -- which would set up a veto showdown this fall. 

Meanwhile, Sen. Ted Cruz, R-Texas, is taking the complaints to a new level, threatening to block State Department nominees unless Obama assures that the U.S. will block the Security Council resolution approving the Iran deal until Congress conducts its review. 

"That [U.S. Ambassador] Samantha Power has already introduced a draft resolution to the Security Council portrays an offensive level of disrespect for the American people and their elected representatives in Congress," Cruz wrote in a letter to Obama.