Lawmakers' approval of a bill to streamline the passage of trade deals through the U.S. Congress will be a "close call," U.S. Agriculture Secretary Tom Vilsack said last week.

U.S. officials are lobbying lawmakers to support legislation allowing the White House to submit trade deals to Congressfor a yes-or-no vote, without amendments, in exchange for setting negotiating goals.

"I think it's a very close call right now," Vilsack said at the annual U.S. Department of Agriculture Outlook Forum, according to trade publication Inside US Trade.

"I think there's still work that needs to be done to make sure that people are comfortable in knowing there's adequate transparency, and understanding and appreciating thatCongress is not surrendering its power to the executive branch."

Opponents of trade promotion authority, or fast-track, include conservative Republicans against granting more authority to the White House and Democrats worried about the impact of trade deals, such as the 12-nation Trans Pacific Partnership (TPP), on jobs.

As part of the lobbying effort, the White House has posted a YouTube video touting the benefits of trade and senior administration officials are visiting towns and cities around the country and speaking to small businesses.

U.S. Trade Representative Michael Froman toured a Mary Kay cosmetics factory inDallas, Texas on Tuesday and Commerce Secretary Penny Pritzker has been to Tacoma, San Francisco, Portland and Seattle.

"Trade promotion legislation is a hard vote to get passed," she said on a media call on Thursday to promote the benefits of trade and exports in Minnesota.

"This is not going to pass by wide margins, it will pass by a small margin, but it will pass because it's the right thing to do."

Experts say fast-track will give trading partners security deals that will not be picked apart in Congress once they are agreed on and is important to get a good deal on the TPP, which is nearing completion.

Trade skeptics are also lobbying lawmakers to reject the bill, which Senate Committee on Finance Chairman Orrin Hatch has said he hopes to introduce this month.

A coalition of 35 religious groups - including Christian, Muslim and Jewish organizations - wrote to members of Congress this week urging them to oppose fast-track.