US President Barack Obama has appealed to members of both Houses of Congress to support the Iran nuclear deal. However, some lawmakers say they fear too many concessions may have been made to Tehran.
Speaking at the White House on Tuesday, Obama warned Republicans against vetoing the deal signed between Iran and international negotiators.
The US president said it would be a mistake for Congress to pass a disapproval resolution that would sink the accord.
Obama said the nuclear agreement moved US-Iranian relations "in a new direction" and said it would be "irresponsible" of Congress to interfere.
"No deal means a greater chance of more war in the Middle East," said Obama in remarks from the White House.
"I have no doubt that 10 or 15 years from now, the person who holds this office will be in a far stronger position with Iran further away from a weapon and with the inspections and transparency that allow us to monitor the Iranian program."
However, numerous Republican figures have threatened to scupper the agreement, which restricts Iran's nuclear enrichment activities for a decade in exchange for the easing of sanctions.
The House of Representatives Republican speaker, John Boehner, said the agreement would only serve to embolden Iran. He added that Obama had "abandoned his own goals" during the negotiations.
"Instead of stopping the spread of nuclear weapons in the Middle East, this deal is likely to fuel a nuclear arms race around the world," Boehner said in a statement.
The Senate Majority Leader, Republican Mitch McConnell said Obama has adopted a "flawed perspective" to the talks: "reaching the best deal acceptable to Iran, rather than actually advancing our national goal of ending Iran's nuclear program."
US lawmakers will have at least 60 days to mull the highly complex agreement, with intense lobbying expected on both sides. Many in the US share Israeli concerns that the deal is too weak.
McConnell said congressional hearings would pay particular attention to the "concessions" that Iran was able to secure from the Obama administration.
Tricky path ahead
A rocky road lies ahead for the deal as it is considered by US lawmakers. While Congress does not have to approve the accord formally, members could seek to thwart Obama by preventing him from waiving the US sanctions. Although the president can veto such actions, this could be overridden if his opponents can muster a two-thirds majority.
"It is incumbent on Congress to review this agreement with the thoughtful, level-headed process an agreement of this magnitude deserves," Reid said.
Fears over enforcement
The nearly 100-page agreement imposes new provisions for the inspection of Iranian facilities and is aimed at keeping Iran from producing enough of the fissile material it would need to make a bomb. While Obama claims it does not excessively tie the hands of the US should Iran fail to comply, many Republicans claim the deal was not sufficiently tough when it comes to enforcement.
An announcement of the deal was made by EU foreign policy chief Federica Mogherini and Iranian Foreign Minister Mohammad Javad Zarif.
While Iran's President Hassan Rouhani has said the negotiations proved that "constructive engagement works," Israel - believed to be the region's only nuclear power at present - has opposed what it calls a "historic surrender."
rc/jil (AP, dpa, Reuters)