WASHINGTON - President Barack Obama on Tuesday secured 42 votes in the US Senate for the international nuclear deal with Iran, more than enough to keep Congress from passing a resolution disapproving of the pact.
Democratic Senators Richard Blumenthal, Gary Peters, Ron Wyden and Maria Cantwell announced they would support the agreement, just as lawmakers returned to Washington from a month-long summer recess.
Forty-two votes is one more than the minimum needed in the 100-member Senate to block a Republican-backed resolution of disapproval of the nuclear deal, announced on July 14.
That would spare Obama the embarrassment of having to use his veto power to protect a deal reached with five other world powers, seen as a potential legacy foreign policy achievement for his administration.
Obama had been guaranteed enough votes to sustain a veto once he reached 34 "yes" votes in the Senate, but backers say avoiding the veto process would send an important message to Iran, and the world: Washington is unified behind it.
"This agreement with the duplicitous and untrustworthy Iranian regime falls short of what I had envisioned. However, I have decided the alternatives are even more dangerous," Wyden said in a statement explaining his support.
White House spokesman Josh Earnest said the administration was "gratified" by the growing support for the nuclear accord.
The last hope of bipartisan Senate support was dashed on Tuesday when Senator Susan Collins, the chamber's last undecided Republican, announced her opposition.
All of the senators supporting the deal are Democrats or independents who caucus with them. Every supporter in the House of Representatives is a Democrat.
Senator Joe Manchin on Tuesday became the fourth Senate Democrat voting against the deal. At least 17 House Democrats have also said they would vote with Republicans against it.
To block the resolution, deal supporters would need at least 41 senators to vote in favour of using the Senate's filibuster procedural rule to keep a disapproval resolution from advancing.
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It was not immediately clear if any would break with Democratic party leaders and oppose a filibuster, but most said they would back the procedural measure.
"If the cloture (procedural) vote becomes in effect the opportunity to vote in support of the agreement, I will vote in favour of closing debate," Blumenthal said.
FIERCE LAST-DITCH LOBBYING
Groups on both sides of the issue were waging fierce last-ditch campaigns to influence senators' votes on the procedural measure.
Given Republican unity against the nuclear agreement, pressure on Democrats for the past two months has been intense, particularly from pro-Israel groups that normally enjoy strong support from members of both parties.
Israeli Prime Minister Benjamin Netanyahu has been a vociferous opponent of the Iran deal, calling it a threat to his country's existence. Republicans invited him to address Congress about his opposition to the deal negotiations earlier this year.
Many opponents argue that the deal offers sanctions relief in exchange for too few nuclear concessions from Iran. They want negotiators to return to the table to push for tougher terms.
However, the five other world powers that reached the deal have made clear they have no intention of resuming talks. They will also ease sanctions, regardless of Congress' vote on the accord, if Iran fulfills its commitments.
Iran denies its nuclear programme aims to produce weapons.
Republicans, who have majorities in the Senate and House, have denounced the idea of using the procedural rule to keep a disapproval resolution from advancing.
They note that Congress voted overwhelmingly earlier this year for the legislation that lets Congress review the nuclear pact.
"I do hope that senators ... will allow us to actually have a vote on the substance of the bill," Senator Bob Corker, the author of the Iran Nuclear Review Act, told reporters.
However, he added that it had always been expected that, under Senate rules, it would take 60 votes to pass a disapproval resolution.
If a resolution of disapproval passed, and Congress overrode Obama's promised veto, Obama would be barred from waiving many US sanctions on Iran, a key component of the deal.
Under the Review Act, which Obama signed into law in May, Congress has until Sept. 17 to pass the resolution. Obama then has 12 days to veto and Congress has another 10 days to try to override his veto. The first congressional votes on the deal are expected this week.
A disapproval resolution is expected to receive the simple majority of votes it will need to pass the House, where Republicans hold 246 of the 435 seats.
House Democratic leaders have been working to marshal the 146 votes to sustain Obama's veto in that chamber, if necessary. By late Tuesday, they had more than 120, all Democrats.