The White House says it is prepared to talk one-on-one with Iran to find a diplomatic settlement to the impasse over Tehran's reported pursuit of nuclear weapons, but there's no agreement now to meet.

National Security Council spokesman Tommy Vietor said Saturday that US President Barack Obama has made clear that he will prevent Iran from getting a nuclear weapon and will do whatever's necessary to prevent that from happening. Vietor said Iran must come in line with its obligations, or else faced increased pressure.

"The onus is on the Iranians to do so, otherwise they will continue to face crippling sanctions and increased pressure," Vietor said in a statement. He noted that efforts to get Iran back to the table with the five permanent members of the U.N. Security Council and Germany - the so-called "P5+1" - continue.

Iran has been a recurring issue in the presidential election campaign and Vietor's statement was released shortly after The New York Times reported Saturday that the U.S. and Iran have agreed in principle for the first time to negotiations. The paper said Iran has insisted the talks wait until after the Nov. 6 election.

Vietor, however, denied that any such agreement had been reached.

"It's not true that the United States and Iran have agreed to one-on-one talks or any meeting after the American elections," he said. We continue to work with the P5+1 on a diplomatic solution and have said from the outset that we that we would be prepared to meet bilaterally."

Obama and Republican presidential candidate Mitt Romney will meet Monday night in a debate focusing on foreign policy and Iran's nuclear ambitions will likely be a topic. Obama has said he'll prevent Iran from acquiring nuclear weapons.

He hopes sanctions alongside negotiations can get Iran to halt uranium enrichment. But the strategy, which began during President George W. Bush's administration, hasn't worked yet. Obama holds out the threat of military action as a last resort.

Romney has accused Obama of being weak on Iran and says the U.S. needs to present a greater military threat.

Despite unprecedented global penalties, Iran's nuclear program is advancing as it continues to defy international pressure, including four rounds of sanctions from the U.N. Security Council, to prove that its atomic intentions are peaceful.

Those sanctions, coupled with tough measures imposed by the United States and European nations are taking their toll, particularly on Iran's economy. Iranian authorities have in recent weeks been forced to quell protests over the plummeting value of the country's currency, the rial. The rial lost nearly 40 percent of its value against the U.S. dollar in a week in early October, but has since slightly rebounded.

U.S. officials say they are hopeful that pressure from the sanctions may be pushing Iran's leaders toward concessions, including direct talks with the United States. But several said on Saturday that they did not believe such discussions would happen any time soon.

If one-on-one talks are to occur, they would likely follow the model that the U.S. has used in six-nation nuclear disarmament talks with North Korea, the officials said.

In those discussions, U.S. negotiators have met separately with their North Korean counterparts but only as part of the larger effort, which also involves China, Japan, South Korea and Russia. Direct U.S.-North Korean talks are preceded and followed by intense consultations with the other members of the group.

However, the direct talks with North Korea have yet to bear fruit and U.S. officials warned that talks with Iran may not yield anything either. If U.S.-Iran talks do occur, they would likely be part of the P5+1 process, which groups the Britain, China, France, Germany, Russia and the United States and is overseen by the European Union. The group has met numerous times with Iranian officials but has yet to achieve any significant progress.

In late September, the group instructed EU foreign policy chief Catherine Ashton to reach out to Iran's top nuclear negotiator, Saeed Jalili, to organize another meeting. No date had been set for the possible resumption of talks.

Iran says its program is for peaceful energy and research purposes but Western nations fear the Islamic republic is determined to develop nuclear weapons and fundamentally reshape the balance of power in the Middle East. That would pose a grave threat to Israel.

Israel has threatened to strike Iran's nuclear facilities if Tehran doesn't stop uranium enrichment a process that can be a pathway to nuclear arms. Israel could decide to strike Iran's nuclear sites on its own, and Israeli leaders say time to act is running out. They have also hinted they would like U.S. support for any such attack.

An Israeli strike on Iran with or without Washington's involvement would likely draw retribution from Tehran including possible attacks on U.S. and Israeli interests overseas or disruptions to the transit of tankers through the Strait of Hormuz, which could send oil prices skyrocketing.

Obama has counseled patience as public as American public support for another Mideast conflict is low with the Iraq war over and the conflict in Afghanistan winding down.