The Obama administration's chief nuclear negotiator, Wendy Sherman, refused on Tuesday to provide a hard deadline for a deal with Iran to prevent it from developing nuclear weapons, The Associated Press (AP) reported.
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 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 November 24, after they were unable to reach a permanent deal by a July 20 deadline.
"The next four months will allow us to determine whether a diplomatic solution is possible," Sherman was quoted as having 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," she added.
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, and would not promise the current extension would be the last.
Sherman 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, according to AP.
The 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 its 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.
Sen. Bob Menendez, D-N.J., called Iran's concessions to date "underwhelming."
"I've been skeptical of the Iranians' sincerity from Day 1 and I cannot say that I am any less skeptical today," said Menendez, the committee chairman, according to AP. He added he'd oppose any further extension of negotiations.
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."