The Obama administration’s chief nuclear negotiator refused Tuesday to provide a hard deadline for a deal with Iran to prevent it from developing nuclear weapons. She vowed to consult with Congress before suspending more economic sanctions on Tehran, but said the administration won’t necessarily seek lawmakers’ approval.

The testimony by the State Department’s Wendy Sherman immediately prompted objections in the Senate Foreign Relations Committee, whose Democratic and Republican members pushed for clear markers as part of the diplomatic effort. World powers and Iran recently committed to a four-month negotiating extension through Nov. 24, an agreement that allows the Islamic republic to recoup $2.8 billion in Iranian assets frozen in overseas bank accounts.

“The next four months will allow us to determine whether a diplomatic solution is possible,” Sherman told the panel. “A comprehensive resolution, if we are able to arrive at one, will benefit people everywhere. It will ease anxiety and enhance security throughout the Middle East. It will reduce the likelihood of a nuclear arms race in the region. It will eliminate the potential threat of nuclear blackmail. It will contribute to the security of Israel, the Gulf states and our partners throughout the region.”

But pressed by senators to outline how long the administration would continue talking and how far it would consider bending to coax Tehran into an accord, Sherman refused to be pinned down. She wouldn’t promise the current extension would be the last. She said the administration would consult lawmakers before waiving more sanctions, but doesn’t need their approval.

Sen. Bob Corker of Tennessee, the top Republican on the committee, described Sherman’s pledge as a “zero commitment.”

Sen. Marco Rubio, R-Fla., was blunter.

“This entire thing is a disaster,” he said.

Iran says its program is solely designed for peaceful nuclear energy generation and medical research. The United States and its partners believe Iran’s uranium enrichment activity, a potential heavy water facility that can produce plutonium and ballistic missile research, all point to a covert weapons program.

An interim deal reached last November and put into place earlier this year provided Tehran up to $7 billion in economic relief for a series of measures to freeze in place Iran’s nuclear advancement. The goal was to reach a final agreement by July 20 but Secretary of State John Kerry and other top diplomats said that while tangible progress had been made, the gaps were still too wide.

Sherman said the administration strongly believes the talks merit additional time.

“We wouldn’t have agreed to an extension if we did not have an honest expectation that we have a credible path forward,” she said. “We still have work to do. We still have time to determine whether we can close the gap between what Iran has said it intends and what it is willing to do.”

Congress would enjoy its greatest leverage if a comprehensive accord is reached.

Lawmakers would essentially enjoy a veto over any final deal because they could place strict limits on Iranian activity in exchange for the revocation of U.S. nuclear-related sanctions.

Permanently scrapping sanctions that are codified in U.S. law would require both chambers of Congress to act. That task would only get harder for the administration if Republicans, who already control the House, seize a majority in the Senate in November’s midterm elections.

(AP)