Erin Kelly, USA TODAY 11:37 a.m. EDT September 2, 2015

Sen. Barbara Mikulski, D-Md.(Photo: Steve Ruark, AP)

WASHINGTON — President Obama on Wednesday secured the congressional support he needs to ensure the Iran nuclear deal cannot be derailed as Maryland Sen. Barbara Mikulski came out in favor of the agreement.

Mikulski's support means 34 Senate Democrats have publicly said they'll vote for the deal. That's enough to sustain a veto by President Obama if Congress passes a resolution of disapproval opposing the pact.

Congress is scheduled to vote on the nuclear deal by Sept. 17.

Secretary of State John Kerry said Wednesday that the agreement will prevent Iran from developing a nuclear bomb. The pact would lift economic sanctions against Iran in exchange for Iran agreeing not to develop nuclear weapons.

"Without the agreement, the Iranians would have several potential pathways to a bomb," Kerry said. "With it, they won't have any."

In a statement, Mikulski, who's retiring after the 2016 elections, said, "“No deal is perfect, especially one negotiated with the Iranian regime. I have concluded that this Joint Comprehensive Plan of Action is the best option available to block Iran from having a nuclear bomb."

On Tuesday, two other Democrats, Sens. Bob Casey of Pennsylvania and Chris Coons of Delaware, endorsed the agreement.

Ten Democrats remain undecided. If seven of them support the deal, Democrats would have enough votes to block the resolution of disapproval from even coming to a vote in the Senate. It is expected to pass the House.

Republicans say Iran cannot be trusted to comply with the agreement and have called for stricter inspection requirements to ensure that Iran does not secretly move forward with the development of a nuclear bomb.

Mikulski said the vote is one of the most serious she has faced in her nearly 30 years as a senator.

"This vote has monumental and enduring consequences," she said.

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