The last remaining undecided US Democratic senator joins the other 41 supporters of the Iran nuclear agreement who have already gained enough power to potentially filibuster Republican push to reject it.

On Tuesday, President Barack Obama secured enough Senate support to block the vote on the Iran accord as three more Democratic senators announced they would vote in support of the deal.

The announcement by Senators Richard Blumenthal of Connecticut, Ron Wyden of Oregon and Gary Peters of Michigan brought the total number of senators who back the agreement to 41.

Later on, Senator Maria Cantwell of Washington announced she would be the 42nd senator to support the deal.All Senate Democrats have now announced where they stand on the Joint Comprehensive Plan of Action (JCPOA) reached between Iran and the P5+1 group of countries in July in Vienna, Austria.

The level of support would potentially block passage of the resolution by paving the way for a filibuster of Republican attempts to disapprove of the nuclear agreement.

The four Democratic senators opposing the deal are Chuck Schumer of New York, Ben Cardin of Maryland, Senator Joe Manchin of West Virginia and Bob Menendez of New Jersey.

Please don't filibuster Iran vote

Meanwhile, US Senate Majority Leader Mitch McConnell (pictured above) called on Democrats not the use a filibuster, which is a tactic that involves legislators obstructing the passage of a bill by speaking at inordinate length when the measure is debated.

"I expect that every senator who voted for [the Iran Nuclear Agreement Review Act of 2015] is now entitled to an up-or-down vote. Not a filibuster or artificial limits on passage, but an important vote on this resolution," said the Republican Senate majority leader.

"The Senate should not hide behind procedural obfuscation to shield the president or our individual views," he added.

Reid offer

Over the weekend, Senate Minority Leader Harry Reid (pictured above) suggested that Democrats would mount a filibuster to prevent the Iran Nuclear Agreement Review Act from reaching the president’s desk for a veto.

However, the Democratic minority leader also offered to allow the Senate to go directly to a vote on final passage, but only if McConnell agreed to a 60-vote threshold for passage, which now seems almost impossible since 42 senators in the 100-member chamber have already announced to vote against the Republican resolution.

"I recently informed Senator McConnell that after a period of robust debate, Democrats would be happy to proceed straight to a final passage vote that is consistent with Senator McConnell’s many statements that important matters in the Senate have ‘for quite some time required sixty votes,’ " Reid said on Saturday. "The choice is up to him."

McConnell on Tuesday said Democrats would probably filibuster the Iran resolution to protect the president.

He said while Obama will be “out of office in a few months, the rest of the country and the world will have to deal with the predictable consequences of the president's deal for far longer than the next year and a half."

Obama victory  

If Democratic senators do not filibuster the Republican bill, President Obama will be forced to veto the resolution disapproving of the agreement if the Senate and House of Representatives both pass such a measure.

Congress has until September 17 to vote on the nuclear deal. A Democratic filibuster in the Senate would be a clear victory for Obama to nip the process in the bud and prevent a chance for the lobbying to kick into high gear.

The Obama administration is set to gain this resounding victory over its opponents, despite the Israel lobby’s massive campaign to defeat the historic nuclear agreement, reached between Iran and the P5+1 -- the US, Britain, Russia, China, France, and Germany -- in Vienna in mid-July.

The American-Israeli Public Affairs Committee (AIPAC) has deployed hundreds of lobbyists on the US Capitol to try to convince lawmakers to vote against the agreement.

According to reports, AIPAC and other pro-Israel lobbying groups have spent at least $40 million on television commercials and other propaganda material to inform the public “about the dangers of the proposed Iran deal.”