President Barack Obama wins a victory in the Senate on re-writing the rules of international trade. (Carolyn Kaster/AP)

President Obama won a big victory for his trade agenda Friday with the Senate’s approval of fast-track legislation that could make it easier for him to complete a wide-ranging trade deal that would include 11 Pacific Rim nations.

A coalition of 48 Senate Republicans and 14 Democrats voted for Trade Promotion Authority late Friday, sending the legislation to a difficult fight in the House, where it faces more entrenched opposition from Democrats.

The Senate coalition fought off several attempts by opponents to undermine the legislation, defeating amendments that were politically popular but potentially poisonous to Obama’s bid to secure the trade deal.

“This is an important bill, likely the most important bill we will pass this year. It’s important to President Obama,” Sen. Orrin G. Hatch (R-Utah), chairman of the Senate Finance Committee and primary author of the bill, said at the close of debate.

TPA’s fast-track provisions would allow Congress, under strict timelines, to consider trade deals with a simple up-or-down vote without any amendments or requirements of a Senate super-majority to end debate. That would help Obama complete the final details of the Trans-Pacific Partnership (TPP), with the other 11 nations, a bloc that represents about 40 percent of the global economy.

If TPA clears Congress, Obama’s negotiators will push to conclude the Pacific trade pact and then send it to Congress for final approval, possibly later this year or early next year. The legislative package also includes new funding for labor training for workers that are certified for having lost their jobs because of foreign competition.

Obama’s aggressive push for the trade agenda has upended his relationship with his long-standing allies in the labor movement, as well as anti-corporate liberal activists who strongly supported his 2008 and 2012 elections. It sparked sharp exchanges, played out in the national media, with a liberal icon, Sen. Elizabeth Warren (D-Mass.), leading to one of Obama’s normally closest allies, Sen. Sherrod Brown (D-Ohio), to question whether he was being sexist for singling her out for criticism.

Unions and progressive activists have mobilized their forces against TPA for more than a year now, believing that defeating the fast-track authority would probably also kill negotiations on the Pacific trade deal.

On Friday, union leaders narrowly lost their bid for passage of an amendment designed to create strict regulation of global currency markets, offered by Sens. Rob Portman (R-Ohio) and Debbie Stabenow (D-Mich.), whose states have been ravaged by losses of manufacturing jobs to foreign competition.

“This amendment is simply a modest enforcement measure that would direct the administration to conduct negotiations in a manner that will push them closer to getting trade done right. We urge you to support it and oppose any language to weaken it,” William Samuel, a top lobbyist for the AFL-CIO, wrote to senators in a “legislative alert” Friday.

Portman, a former trade representative facing a difficult 2016 reelection campaign, locked arms with Democrats in a bid that was designed as a get-tough gesture toward China, which some have long accused of manipulating its currency to make its exports cheaper. “I want you to be able to tell your workers you not only disagree with currency ma­nipu­la­tion, you want to be able to do something about it,” he said during debate.

However, Treasury Department officials warned that the Portman proposal would prompt a presidential veto, because the other nations would potentially abandon the TPP talks. In the hours leading up to Portman’s vote, Obama worked the phones with wavering senators to defeat the measure, relying heavily on his usual foes — Senate Majority Leader Mitch McConnell (R-Ky.) and his top lieutenants — to round up 51 votes to narrowly defeat the measure.

“This is an important bill, likely the most important bill we will pass this year. It’s important to President Obama,” Sen. Orrin G. Hatch (R-Utah), chairman of the Senate Finance Committee and primary author of the bill, said. (Susan Walsh/AP)

“President Obama will veto any TPA bill that contains this amendment. A vote for Portman-Stabenow is also a vote to kill TPP,” Hatch said just before the vote on the amendment.

In the end, 41 Republicans and 10 Democrats defeated the amendment, which was considered the last major hurdle to securing Senate passage of the legislation.

On the final roll call, five Republicans joined 32 Democrats in opposing TPA — an odd collection that ranged from Minority Leader Harry M. Reid (D-Nev.) and his top two lieutenants to staunch conservatives such as Sen. Rand Paul (R-Ky.). “Congress is forgetting its duty: to improve jobs and wages for Americans,” Sen. Jeff Sessions (R-Ala.), one of the most conservative senators, said in a statement.

House Speaker John A. Boehner (R-Ohio) has said that the TPA bill will come up at some point in June, after his chamber returns from a 10-day break that began Thursday.

In perhaps the most unusual alliance in the debate, Obama’s trade agenda will soon rest largely in the hands of Rep. Paul Ryan (R-Wis.), who was the Republicans’ 2012 vice presidential nominee.

Now chairman of the Ways and Means Committee, Ryan is leading the push to secure as many votes as possible from the Republican side of the aisle for Obama’s fast-track authorities on trade deals. He has been working with Boehner’s leadership team convening meetings with Republicans to educate the dozens of junior lawmakers who have never considered a trade deal like the potential Pacific Rim pact.

Just 55 members of the House were in office during the 1993 debate for the North American Free Trade Agreement, and nearly 140 lawmakers — a third of the entire House — have never voted on any trade deal before. The last trade deals, with Panama, Colombia and South Korea, were approved in October 2011.

Mike DeBonis contributed to this report.