Senator Chuck Schumer, an influential New York Democrat, said he will break with President Barack Obama and oppose the Iran nuclear agreement now under review by US lawmakers.

"I will vote to disapprove the agreement, not because I believe war is a viable or desirable option, nor to challenge the path of diplomacy," Senator Schumer said in a statement Thursday night. "It is because I believe Iran will not change, and under this agreement it will be able to achieve its dual goals of eliminating sanctions while ultimately retaining its nuclear and non-nuclear power."

Senator Schumer, who's in line to become his party's next leader, may be more consequential than any of the Senate Democrats who are still undecided over whether to back the deal. His clout in the chamber gives him the power to bring other lawmakers along.

Senator Schumer, who's in line to become his party's next leader, may be more consequential than any of the Senate Democrats who are still undecided over whether to back the deal. AP

Congress has until the end of the day September 17 to review the accord reached between the US, Iran and five other world powers. If lawmakers pass a resolution of disapproval -- the likely outcome in the Republican-led House and Senate -- Obama has said he will veto it.

The White House is counting on having enough Democrats backing the deal to sustain a veto, which would stand unless two-thirds of Congress voted to override it.

Bloomberg