House Democrats will provide the necessary support to finalize President Obama's nuclear deal with Iran, House Minority Leader Nancy Pelosi (D-Calif.) predicted Thursday.

Asked if the Democrats could sustain a promised veto of the Republicans' expected disapproval measure, Pelosi didn't hesitate.

"Yes," she replied.

Pressed about the reason she's so confident, she said: "Because of the nature of the agreement."

GOP leaders in both chambers, who have hammered the agreement as essentially an endorsement of Iran's nuclear weapons program, are expected to vote in September on legislation disapproving it — resolutions Obama has vowed to veto.

That scenario sets the stage for Republican attempts to override the veto — votes that would require Democratic support to reach the two-thirds majority needed for passage.

A number of liberal Democrats, such as Pelosi, have come out in strong support of the agreement, saying it presents the best opportunity for the U.S. and its allies to prevent Iran from building nuclear arms.

"There is simply no acceptable alternative to this deal," Reps. Luis Gutierrez (D-Ill.) and John Yarmuth (D-Ky.) wrote this week in an op-ed in The Hill.

A handful of others have already announced their opposition, warning that the deal simply doesn't go far enough to ensure that Iran doesn't build weapons or use the influx of cash from sanctions relief to fund terrorism abroad.

"[T]he deal before us now is simply too dangerous for the American people," Rep. Grace Meng (D-N.Y.) said Wednesday in a statement. "I have every confidence a better deal can be realized."

Most House Democrats have not played their hand, saying they want to use the 60-day window to talk to experts and constituents about the agreement.

Pelosi on Thursday hailed Obama for keeping the global negotiators at the table, characterizing the deal as "a diplomatic masterpiece." She said House Democrats are lining up behind the deal in numbers sufficient to uphold a veto of the expected Republican effort to sink the deal.

"So where does my confidence spring from? First of all, from the quality of the agreement. Second of all, to the seriousness and thoughtfulness with which my colleagues have approached this," Pelosi said.

"More and more of them have confirmed to me that they will be there to sustain the veto. They've done this not blindly, but thoroughly, and [spent] the last two-and-a-half weeks reviewing the documents. … And it's really pretty exciting."

Pelosi alluded to the strong opposition from well-heeled interests vowing to spend millions of dollars in August on campaigns attacking the deal as a threat to national security. But she predicted members would ignore the noise and focus on the details of the agreement.

"The outside will have endless money — $40 million to spend on TV and going door to door to poison the well on this," she said. "[But] our members have a firm foundation on why they support this. I feel confident."

By The Hill