U.S. President Barack Obama secured a major victory on Tuesday in the congressional fight over the Iran nuclear deal.

Obama gained 41 Senate votes, potentially enabling a filibuster and thus preventing a vote on a Republican-backed resolution rejecting the agreement.

Senators Richard Blumenthal (D-CT), Gary Peters (D-MI) and Ron Wyden (D-OR) all announced their support for the Iran deal on Tuesday. With an overwhelming number of Senate Democrats in favor, they can now kill the disapproval resolution outright in the Senate and protect Obama from having to use his veto pen.

"This agreement with the duplicitous and untrustworthy Iranian regime falls short of what I had envisioned," Wyden said in a statement announcing his support for the agreement. "However, I have decided the alternatives are even more dangerous."

"This is not the agreement I would have accepted at the negotiating table,'' Blumenthal told reporters. "But I am convinced there is no better deal available now."

“Despite my serious concerns with this agreement, I have unfortunately become convinced that we are faced with no viable alternative. Peters said in a statement.

Also on Tuesday, Democratic Senator Joe Manchin of West Virginia said he will oppose the nuclear deal with Iran. Manchin said the Iranian regime has shown no signs of changing its behavior and the deal involving world power does "nothing to guarantee that behavior changes."

Manchin is the fourth Democrat to oppose the international accord, joining Sens. Chuck Schumer of New York, Bob Menendez of New Jersey and Ben Cardin of Maryland.

Iran deal vote tally: Full list of U.S. Senators and where they stand

Congress returns to work on Tuesday and the Iran deal is the first order of business.

It is not clear at this stage whether all the 41 Senators who announced support for the agreement also support a filibuster. Democratic Senator Chris Coons has already hinted that, despite his support for the agreement, he would like to see it voted on in the senate.

However, even if Coons doesn't support a filibuster, Obama will be able to rely on the vote of the Democratic Senator from Washington Maria Cantwell, if she announces her support for the agreement, as expected.

The support of the 41 senators for Obama is another blow to the efforts of the Republicans, the pro-Israel lobby AIPAC, Prime Minister Benjamin Netanyahu and Israel's ambassador in Washington Ron Dermer to block the agreement. Despite all the pressure on them, only 10 Democratic senators – and only two of the 10 Jewish senators – have come out against the agreement.

The voting process in both the senate and the house is expected to be completed by September 17. If a vote is held in the senate it is likely to happen by Thursday. The Republicans, for their part, are interested in holding the vote on Friday September 11, in order to leverage the sensitivity of the date to pressure the Democratic lawmakers.

In Israel, Knesset member Tzipi Livni of the Zionist Union said that in light of the fact that Obama had achieved a blocking majority, Netanyahu needed to act immediately to minimize the damage that has already been done to ties with the U.S.

Yesh Atid leader Yair Lapid said that the support by Democratic senators is proof of Netanyahu's failure. "It seems Netanyahu was wrong all along," he said.

The Associated Press contributed to this report.