News Analysis: U.S., Iran head toward nuke deal, but U.S. Congress could block

The U.S. and Iran are reportedly nearing a deal on Tehran's nuclear program, but it remains unknown whether the U.S. Congress will undermine the agreement by refusing to lift the sanctions that have ruined Iran's economy.

The U.S. and Iran have in recent months been engaged in talks over the latter's controversial nuclear program, which some Western critics say is intended to build nuclear weapons, although Iran maintains the program is peaceful.

But while the White House may be nearing a deal with Tehran, the Republican-led U.S. Congress may butt heads with U.S. President Barack Obama over a few crucial details, experts said.

A key disagreement between the U.S. and Iran is the level of access that inspectors will have to Tehran's nuclear program. The Republican lawmakers want international inspectors to have full, unfettered access to all of Iran's nuclear facilities, including military sites.

But if those terms are not met, the Republicans could scuttle the deal by refusing to lift the sanctions, whether the White House likes it or not. If the U.S. Congress takes that road, Iran is highly unlikely to grant the West any access to its nuclear sites whatsoever, experts said.

"The Congress can undermine any deal with Iran by refusing to lift the sanctions," Brookings Institution's senior fellow Darrell West told Xinhua.

"Without that approval, Iran will say the U.S. broke the deal and will not open up its enrichment facilities," West said.

"The Republicans may not approve any agreement that does not eliminate all enriched uranium and (does not) provide inspections of all nuclear sites. That will be difficult for the administration to deliver," he said.

They are blasting the deal in the works as a boon for Iran but a bust for the U.S., and accuse the Obama administration of weakening its stance by the day.

In a recent op-ed for U.S. newspaper Politico, Senate Majority Leader Mitch McConnell wrote that the Obama administration should "pause negotiations, take a step back and re-examine the point of the talks in the first place."

This reflects Republicans' worries that the U.S. position is weakening and that Iran will get everything it wants while the U.S. gets nothing in return.

As for Iran, the Islamic republic's negotiators are vulnerable to having any deal scrapped by Iran's Supreme Leader Ayatollah Ali Khamenei, who ultimately has the final say, experts said.

David Pollock, senior fellow at the Washington Institute for Near East Policy, told Xinhua there have been cases where negotiators reached an agreement but then took it back to Tehran and saw it vetoed by Khamenei.

For Tehran, it is imperative to get rid of the sanctions that have wrecked its economy and caused its currency to plummet, but it remains unknown when and just how much sanctions will be lifted if a deal is cut.

The U.S. has said sanctions would be lifted over time and parallel with the compliance of provisions in the agreement. But it remains unclear how long that would take.

"It might be six months, it might be a year, it might be more," Pollock said, adding that that depends on how long it will take Iran to comply and satisfy the International Atomic Energy Agency and others that it is actually carrying out the terms of the agreement.

There is also the question of a so-called signing bonus -- Tehran has a lot of money around the world that has been frozen by sanctions, and it has been allowed to access some to it. But it is possible, although not sure, that all of those accounts will immediately be unfrozen after a deal is signed, some experts noted.

The talks missed a deadline at the end of last month but negotiators are feverishly working to meet the extended deadline of July 7.

Over the weekend, Iran also made an effort to sweeten the deal, vowing to help with issues such as the growing threat from the Islamic State. The Islamist terror group has taken vast swaths of territory in the Middle East and the U.S. has been waging an air bombardment campaign against the group for months. Endi