U.S. Trade Representative Michael Froman said on Thursday a Pacific trade agreement can be wrapped up in months and urged lawmakers to quickly move ahead with key trade legislation.

Froman said although there was no firm deadline to conclude the 12-nation Trans-Pacific Partnership, "we do feel that we can close this out in a very small number of months."

Some countries are demanding Congress approve legislation to streamline the passage of trade deals before closing the TPP, sources close to the negotiations told Reuters.

But Republicans and Democrats are still negotiating the final form of the bill, which would allow lawmakers to set negotiating objectives in exchange for a yes-or-no vote, with no deal expected until next month.

"We are encouraging Democrats and Republicans to work together to reach agreement on a bill that can get bipartisan support and to move that ahead in parallel as soon as possible," Froman said at the National Council of Textile Organizations' annual conference.

The timing of the two is tricky. Many Republicans want fast-track legislation done before TPP and some warn they will not support the TPP if so-called trade promotion authority is not in place before a deal is reached.

But some Democrats - including the party's senior member on the House of Representatives' committee responsible for trade, Sander Levin - want to focus on the content of the TPP and insist getting the deal right must take priority.