This post has been updated.

Ahead of the Senate Finance Committee’s first hearing on three pending trade deals, all 11 Republicans on the panel issued a letter to President Obama Thursday outlining their opposition to the administration’s inclusion of a program aimed at aiding workers who have lost their jobs due to outsourcing.

“We are concerned about last minute attempts to include provisions expanding Trade Adjustment Assistance in the South Korea FTA implementing bill,” the 11 Republicans wrote in the letter. “We believe such actions are beyond the scope of TPA authority and unduly infringe on the rights of Members of the Senate to carefully weigh and debate the merits of TAA.”

The letter follows a warning Thursday morning from the panel’s leading Republican, Sen. Orrin Hatch (R-Utah), that the inclusion of the Trade Adjustment Assistance program in the South Korea deal could imperil passage of the trade pacts.

“This action abuses long-standing rules, procedures and precedents governing the delegation of trade negotiating authority from the Congress to the President and puts a successful vote on the South Korean FTA — the largest trade pact negotiated in more than a decade — at risk,” Hatch’s office said in the memo.

The statements are the strongest warning to date that the deal announced Tuesday by the White House and congressional negotiators on the Colombia, Panama and South Korea trade deals may face a bumpy road to congressional approval.

The Senate Finance Committee is slated to meet at 3 p.m. Thursday to begin working its way through the dozens of amendments to the deals submitted my members of both parties. The House Ways and Means Committee will likely hold a meeting on the trade pacts next week at the earliest, after the House returns from recess.

Republicans in both chambers had been urging Obama to submit the deals to Congress, but after Tuesday’s announcement, GOP leaders charged that the attachment of a three-year renewal of the Trade Adjustment Assistance program to the South Korea deal was a “highly partisan” move.

“Including unrelated and highly controversial provisions, like the TAA spending program, into the Korean trade agreement violates the letter and spirit of this law,” Hatch’s office said Thursday.

The White House and Democrats have defended the deals.

“The addition of Trade Adjustment Assistance to the Korea Free Trade Agreement is entirely consistent with precedent,” a Senate Finance Committee Democratic aide said Thursday. “As you may recall, Trade Adjustment Assistance was added to the implementing language of the NAFTA agreement — a trade agreement many of the current members of the Senate supported in the past.”

Meanwhile, some Democrats are also expressing opposition to the deals. House Democratic Conference Chairman John Larson (Conn.) on Thursday announced that he would not back the Colombia deal over concerns on labor rights.

“I am extremely disappointed that congressional Republicans have prevented any meaningful reference to the Action Plan Related to Labor Rights in the Colombia Free Trade Agreement implementing legislation that we’re being asked to consider,” Larson said in a statement, adding that he would oppose the legislation in its current form.

Also on Thursday, the U.S. Chamber of Commerce released a letter urging Congress to pass the deals and expressing its support for the inclusion of TAA with the deals, contending that “the resulting legislation is respectful of the difficult fiscal circumstances facing our country, and we believe it deserves support.”

“These trade agreements would create tens of thousands of jobs for American workers and farmers – and businesses both large and small – all across the nation,” the letter reads. “At a time when millions of Americans are out of work, the agreements would level the playing field for American exporters and create real business opportunities for American businesses and employers.”