President Barack Obama has officially secured enough support in Congress behind the U.S.-Iran nuclear deal to ensure that the historic agreement can be approved.

Under the deal, the U.S. and four other major world powers agreed to lift Iran's economic sanctions. In turn, the Islamic republic vowed to limit its nuclear program for the next 10 years.

In order to garner support for the agreement, Obama also wrote an open letter to Congress promising that the U.S. would take military action if Iran decided not to uphold its end of the bargain.

"Should Iran seek to dash toward a nuclear weapon, all of the options available to the United States -- including the military option -- will remain available through the life of the deal and beyond," Obama said in a letter, according to The New York Times.

On Wednesday, Democrat Barbara Mikulski became the 34th senator to back the deal, giving the Obama administration enough votes to override any resolution of disapproval.

"No deal is perfect, especially one negotiated with the Iranian regime," said Mikulski in a statement, according to BBC News. "I have concluded that this Joint Comprehensive Plan of Action is the best option available to block Iran from having a nuclear bomb."

This means that Obama has enough votes to back a veto if Republicans decide to disapprove the deal as expected.

Although Obama has enough votes to pass the deal, Secretary of State John Kerry said the administration will continue to try to sway more lawmakers to support the agreement. If Obama can secure 41 votes, then he will have enough to filibuster the bill and prevent it from being presented to the Senate for a final up-or-down vote.

"Thirty-four votes are obviously enough votes for the president's veto to be upheld," said Kerry on CNN. "That is not satisfactory for us. We do want to try to go further. We'll continue to persuade."

Almost all congressional Republicans have come out against the agreement, arguing that Iran cannot be trusted and will likely continue to build nuclear warfare once the sanctions are lifted.