WASHINGTON - Secretary of State John Kerry urged Congress on Tuesday to put off more sanctions against Iran at this time, saying "this is a very delicate diplomatic moment" to seek a peaceful solution to the issue of preventing Tehran from gaining nuclear weapons.
Kerry, appearing before the House Foreign Affairs Committee, sought to reassure lawmakers about the Obama administration's commitment to preventing a nuclear armed Iran, but underscored the importance of international diplomatic efforts that have so far produced a temporary agreement curbing its nuclear program.
"Iran will not acquire a nuclear weapon," he said, stressing that declaration was the centerpiece of President Barack Obama's foreign policy.
But Kerry said he had "serious reservations" about Iran's willingness to negotiate a comprehensive deal to curb its nuclear ambitions if such an agreement ended Tehran's nuclear program completely.
The current internationally brokered accord expires in six months. It eases some economic sanctions in return for limiting aspects of Iran's nuclear program.
Kerry, appealing for the current diplomatic path to proceed as designed, is facing pressure from some members of Congress -- Republicans and Democrats -- to push harder on sanctions as a way to force the new Iranian leadership's hand over the long term on the nuclear issue.
Iran knows it will face increased sanctions if broader negotiations fail Kerry said, adding that it would be "gratuitous" for Congress to act now on further sanctions.
Israel opposes the interim deal because it allows Iran -- a longtime enemy of the Jewish state -- to continue enriching uranium needed to develop nuclear weapons.
Prime Minister Benjamin Netanyahu has made clear that Israel would attack Iran's nuclear facilities if it felt threatened, and the negotiations are considered an effort to avoid a possible military confrontation in the volatile Middle East.
And some members of Congress agree that tougher measures are needed.
"We are facing an immoral and very dangerous regime in Iran, one nearing a nuclear weapon," House Foreign Affairs Committee Chairman Ed Royce of California said in a written statement ahead of Kerry's appearance.
"I am hard pressed to understand why we'd be letting up sanctions pressure at the very time its economy is on the ropes without getting an agreement which stops its centrifuges from spinning."
Iranian officials have long said the country's nuclear intentions were peaceful. They also warned any new sanctions would scuttle the interim agreement, noting that language in the document specifies no new ones can occur.
At the State Department, spokeswoman Jen Psaki said on Monday new sanctions now -- even ones that don't take effect for six months -- could derail the agreement that involves the other four permanent members of the U.N. Security Council, as well as Germany and Iran.
"We are hopeful that Congress will ... will not put in place new sanctions because, as we've discussed, it would certainly put the entire process at risk," Psaki said.
A bipartisan group of Senators is close to an agreement on tougher sanctions, CNN has learned, but it is not clear whether the Democratic majority would even bring the matter up for a vote.
That deal, if it comes together, would include a new round of sanctions to begin in six months and would bar the enrichment of uranium. It would permit commercial nuclear power as long as it was monitored by the international community.
The bipartisan group includes Democrats Chuck Schumer of New York and Robert Menendez of New Jersey and Republicans Lindsey Graham of South Carolina and Mark Kirk of Illinois -- all strong supporters of Israel.
"I hope this week we will introduce a bipartisan third round of sanctions," Graham told CNN in an interview on Monday. "We'll do sanctions tied to the end game where the relief will only come if they stop the enrichment program, dismantle the reactor and turn over the enriched uranium."
Sources told CNN the group still has work to do to finalize its plan, which is opposed by the White House.
"The administration's preference is for us to do nothing," one source said, while another said "they're fighting us tooth and nail."
Obama said over the weekend that he would accept a peaceful nuclear program in Iran, including modest uranium enrichment.
Royce said in his prepared statement that the key issue is whether an eventual final agreement negotiated on the world stage with Iran would permit it to "manufacture nuclear fuel."
"Unfortunately, the interim agreement reads 'yes,' it will," Royce said. "My concern is that we have bargained away our fundamental position, which is enshrined in six U.N. Security Council Resolutions -- that Iran should not be enriching and reprocessing -- in exchange for a false confidence that we can effectively check Iran's misuse of these key nuclear bomb-making technologies."
He noted that Iran recently announced plans to continue working on centrifuge technology and constructing a plutonium reactor, adding: "What does this say about Iran's intentions?"
Royce also said Iran has "a history of deceiving the international community about its nuclear program, and is pursuing a ballistic missile program in violation of U.N. Security Council Resolutions," adding that it "simply can't be trusted with enrichment technology, because verification efforts can never be foolproof."
Psaki said the purpose of the interim deal was to see if Iran would be true to its word.
"If the Iranians fall back on any part of the agreement, if they don't abide by the agreement or they violate it, then we would certainly be leading the charge to put more sanctions in place," she said.
"We could put new sanctions in place very quickly at the end of six months if we wanted to," Psaki also said. "And if we are at that point because Iran has not abided by the agreement, we haven't moved the process forward, certainly (Kerry) would be supportive of that."