The White House sent Chief of Staff Denis McDonough and a small army of administration officials to Capitol Hill Wednesday to talk fast-track trade authority with House Minority Leader Nancy Pelosi.

House Republicans say they expect to put the Senate-passed trade measure on the floor before the end of the week. It would allow for an up-or-down vote on future trade deals, most notably the Trans-Pacific Partnership, which major liberal groups oppose. The vast majority of Pelosi's Democrats are expected to vote against the president, but the White House is still trying to round up as many as 20 to 25 defectors to join hands with Republicans.

With little fanfare, McDonough walked into Pelosi's second-floor Capitol Building office with National Economic Council director Jeff Zients, US Trade Representative Mike Froman, Labor Secretary Tom Perez, and legislative affairs specialist Amy Rosenbaum at about 3 pm.

The meeting was "part of the administration's ongoing engagement with Congress on the president's trade agenda," a White House official said. Pelosi spokesman Drew Hammill declined to discuss the meeting; the minority leader has so far kept her cards close to the vest on both fast-track authority and the TPP deal as a whole.

Labor groups have put tremendous pressure on Democrats to oppose fast-track authority, which would pave the way for consideration of the Pacific Rim trade deal. The AFL-CIO's legislative director, Bill Samuel, circulated a letter to House members on Wednesday urging them to vote against a companion measure funding assistance programs for workers hurt by international trade, on the grounds that there's too little money and that it would be funded by a Medicare cut:

On behalf of the AFL-CIO, I urge you to vote against the Trade Adjustment Assistance (TAA) proposal that will be considered during the Fast Track debate. Although the AFL-CIO supports renewal of a comprehensive and well-funded TAA, a vital program to help retrain workers who lose jobs to trade, the version being considered falls short in several areas.

As Greg Sargent of the Washington Post explained last week, House liberals believe the TAA issue could derail the fast-track bill. If TAA fails, or if it's sweetened to please liberals, the fast-track bill would be subject to a House-Senate conference to iron out the differences between the chambers. That could be a very messy process.