For the second time in nearly three weeks, America’s secretary of state, John Kerry, changed his travel schedule on Friday to attend nuclear talks with Iran in Switzerland. At home, lawmakers were growing restless.

The last time Kerry attended the negotiations in Geneva between the world’s major powers and Iran, a deal seemed at hand but failed to materialize when the five permanent members of the United Nations Security Council plus Germany refused to recognize Iran’s right to enrich uranium. France also walked out, reportedly because the closure of a key plutonium plant was not part of the agreement.

Diplomats are keen to avoid a similar breakdown this time around. Both sides insist that the talks are among the most serious that have taken place since Iran’s nuclear program became a global concern. Both also understand that the clock for an agreement is ticking.

To illustrate just how much pressure the negotiators are under this weekend, the most senior members of the United States Senate united in drawing a rhetorical “line in the sand,” arguing that more economic sanctions against Iran were needed and America should be careful not to make too many concessions.

The Senate’s top Democrat, Harry Reid, otherwise a reliable ally of President Barack Obama’s, signaled his intention on Thursday to support and move through a bipartisan sanctions bill during remarks.

“We all strongly support those negotiations, hope they will succeed, and want them to produce the strongest possible agreement,” Reid said. “But, the Senate must be prepared to move forward with a new bipartisan Iran sanctions bill when the Senate returns after Thanksgiving recess. And I am committed to do so.”

Thankfully for the administration, Reid purposely delayed consideration of any new sanctions this week while negotiations in Geneva continued. President Obama and his top aides all lobbied the Senate to do just that, if only for the purpose of maintaining a constructive atmosphere with the Iranians without the threat of more economic sanctions poising the environment. This seems to be have been the best Obama’s top ally in the Senate could do. Regardless of whether an interim agreement is signed, it is now virtually assured that some members of Congress will debate and try to pass another Iran sanctions bill next month.

Reid’s announcement came on the day a bipartisan group of fourteen senators pledged their commitment to another round of comprehensive sanctions. Among them were third most powerful Democrat in the Senate, Charles Schumer of New York, as well as the party’s Foreign Relations Committee chairman, Robert Menendez of New Jersey.

When combined with an amendment that would limit the Obama Administration’s power to lift sanctions before certain conditions are met — such as a complete halt to Iran’s uranium enrichment activities — the president faces a legislature that is bent on squeezing as many compromises out of the Iranians as possible. Members of Congress are sending a message to the White House that any nuclear pact that is struck with Iran must meet their own standards.

As the world has seen during the last ten years that narrowing the gaps to a point where an interim agreement with the Iranians on their nuclear program can be reached is a tediously difficult undertaking. The threats coming out of the United States Congress this week might have just made the job a bit harder yet.