The heightened rhetoric came as U.S. Secretary of State John Kerry was to meet behind closed doors Wednesday with members of the Senate Banking Committee, which is weighing new sanctions against Iran's energy and financial sectors, similar to a measure approved by the House in August.
Kerry will appeal to skeptical lawmakers of both parties to wait at least a week before considering the new wave of punitive sanctions, State Department spokeswoman Jen Psaki said.
He will ask them to put the sanctions a "temporary pause" to give the international community time to try to finalize a deal, after failing early Sunday to produce an interim agreement on limiting Tehran's nuclear program.
The United States and the four other permanent U.N. Security Council members -- Britain, France, Russia and China -- plus Germany, plan to meet again with Iran in a week to pick up where the failed Geneva, Switzerland, talks left off.
The congressional pause would seek to make sure "our legislative strategy and our negotiating strategy are running hand in hand," Psaki told reporters Tuesday.
Adding new layers of punitive sanctions on the Persian Gulf country would likely seriously complicate the new talks and strengthen hardliners in Tehran who want to see the collapse of Iranian President Hassan Rouhani's diplomatic initiative, diplomats say.
Vice President Joe Biden was expected to engage with lawmakers as well, British newspaper The Guardian said.
The White House views Biden, a former senator from Delaware, as a legislative deal closer.
The proposed six-month interim deal, which did not come to pass Sunday despite earlier diplomatic statements suggesting an accord was likely, would temporarily freeze some of Iran's nuclear programs in exchange for a partial easing of Western sanctions.
Washington and many allies, including Israel, maintain Iran is covertly trying to develop a capacity to build nuclear weapons, a charge Tehran denies.
The White House echoed State Department comments, but escalated the war of words.
Holding off on sanctions "is a decision to support diplomacy and a possible peaceful resolution to this issue," spokesman Jay Carney told reporters at the White House.
"The American people, justifiably and understandably, prefer a peaceful solution that prevents Iran from obtaining a nuclear weapon," he said. "And this agreement, if it's achieved, has the potential to do that.
"The American people do not want a march to war," he said.
"And it is important to understand that if pursuing a resolution diplomatically is disallowed or ruled out, what options then do we and our allies have to prevent Iran from acquiring a nuclear weapon?" Carney said.
"Short of an agreement, Iran will continue to make progress in its nuclear program," he said.