WASHINGTON (AP) — The hardest sell for President Barack Obama will be persuading members of his own party to back a bipartisan agreement on global U.S. trade policy.

Longtime divisions in the Democratic ranks broke open Thursday when top congressional lawmakers finally reached a long-sought deal that would pave the way for the broadest trade policy pact in years. Under the agreement, Obama would be allowed to negotiate trade accords for Congress’ review and move forward with talks on a sweeping partnership with 11 Pacific nations.

Obama quickly said he would sign the bill if Congress passed it.

“It’s no secret that past trade deals haven’t always lived up to their promise,” Obama said in a statement. “And that’s why I will only sign my name to an agreement that helps ordinary Americans get ahead.”

A feud erupted among liberal and pro-business Democrats over the deal’s potential for creating or subtracting American jobs.

“Over and over again, we’ve been told that trade deals will create jobs and better protect workers and the environment,” said Sen. Bob Casey, D-Pa. “Those promises have never come to fruition.”

Under the legislation, Congress gets an up-or-down vote on any such deals, but in exchange cannot make changes — a concern for labor, environmental and other interest groups. The divisions hang over 2016 presidential politics, too, as Democratic contender Hillary Rodham Clinton kicks off her campaign to unite the party.

House Speaker John Boehner, R-Ohio, applauded the deal but said much of the burden of its success rests with Obama.

“He must secure the support from his own party that’s needed to ensure strong, bipartisan passage,” Boehner said in a statement that was echoed by the U.S. Chamber of Commerce.

It was the second time this week that Obama looked into the maw of opposition from his own party over a rare bipartisan accord. On Tuesday, the Senate Foreign Relations Committee unanimously approved a bill that would give Congress the right to review and possibly reject any deal he strikes over Iran’s nuclear capability. Recognizing the futility of fighting, the administration abruptly announced the president would sign the legislation.

Two days later, Sens. Orrin Hatch, R-Utah, and Ron Wyden, D-Ore., and Rep. Paul Ryan, R-Wis., announced a bipartisan accord on the president’s authority to negotiate trade agreements. For Obama, the “fast track” legislation comes at an opportune time. He’s negotiating the Trans-Pacific Partnership, which proposes a trade agreement involving the United States, Japan, Vietnam, Canada, Mexico and seven other Pacific rim nations.

But some Democrats and labor unions say such measures facilitate agreements that wind up destroying jobs in the U.S. and creating jobs in nations that lack the environmental and worker safety protections that exist in the United States.

Teamsters General President Jim Hoffa said the bill “would allow secret trade pacts to sail through Congress with no chance to alter them. That’s bad for American workers as well as their families.”

The Obama administration rejects those claims, and says U.S. goods and services must have greater access to foreign buyers.

Sen. Sherrod Brown, D-Ohio, said the agreement marked only a start and could be derailed by amendments that might be added when lawmakers consider the bill in committees or on the floor.

“Negotiating objectives without enforcement mechanisms don’t get you very far,” Brown told reporters.

Rep. Sander Levin of Michigan, the top Democrat on the House Ways and Means Committee, said the bill “puts Congress in the back seat and greases the skids for an up-or-down vote after the fact. Real congressional power is not at the end of the process, it is right now when the critical outstanding issues are being negotiated.”

Hatch said he expects the committee to consider the legislation next week.

Traditionally, trade legislation has also been accompanied by a parallel bill that provides funding under the Trade Adjustment Assistance program for American workers who are adversely affected by international accords. Wyden and Sen. Susan Collins, R-Maine, unveiled the parallel bill shortly after the trade agreement was announced.

Wyden also introduced separate legislation to renew an expired health care tax break for workers eligible for trade adjustment assistance. The bill would provide a tax credit equal to 72.5 percent of the cost of health insurance.