Straddle carriers move containers in this aerial photograph taken above the Uiwang Inland Container Depot (ICD) in Uiwang, South Korea, on Monday, March 30, 2015. South Korea is scheduled to release trade figures on April 1. Photographer: SeongJoon Cho/Bloomberg

The U.S. Chamber of Commerce formally endorsed President Obama's Pacific Rim trade accord Wednesday, becoming the third major business association to support the 12-nation Trans-Pacific Partnership this week.

The backing from the nation's largest business coalition is a boost to the administration's efforts to rally the private sector behind the deal, which represents the largest regional trade pact in U.S. history. The Chamber joins the National Association of Manufacturing and the Business Roundtable in issuing formal endorsements this week.

Though the support of all three groups was not unexpected, their roles in helping the Obama White House lobby Congress to pass the deal is considered crucial, particularly in convincing Republican leaders to move forward with a final ratification vote this year.

Some GOP leaders, including Senate Majority Leader Mitch McConnell (R-Ky.), have expressed concerns about provisions related to tobacco and pharmaceuticals, and McConnell has suggested the vote could be delayed until after the Nov. 2016 elections or even until after Obama leaves office next January.

“No trade agreement is perfect, and the TPP is no exception," Chamber President Thomas J. Donohue said in a statement. "However, the benefits of a trade agreement lie in how it is interpreted, implemented, and enforced. With that in mind, we’re rolling up our sleeves to work with the administration, Congress and our TPP partners to ensure the agreement is implemented in a way that maximizes its commercial benefits, including market access, rules, and intellectual property protections. We intend to see this job through to the end—to the agreement’s entry-into-force and beyond."