WASHINGTON, Nov. 21 (Xinhua) -- U.S. House Speaker Nancy Pelosi on Thursday cast doubt on the possibility of Congress passing a new North American trade deal, known as the U.S.-Mexico-Canada Agreement (USMCA), by the end of this year.

"I'm not even sure, if we came to an agreement today, that it would be enough time to finish, but it just depends on how much agreement we come to," Pelosi said during her weekly news conference.

"There's a lot of writing and conversations with Canada, with Mexico, on the basis of what we might come to agreement on, in terms of a change in the actual treaty and in the actual agreement," she said.

It will "take time to write" the implementing bill and then bring it to the floor for a vote, the House speaker said, adding she is "eager to get this done."

"I don't want us to miss any opportunity to have a bill that I think could be a template for the future, because globalization is a reality," she said.

House Democrats have been working for months with Trump administration officials to negotiate changes to the USMCA in four main areas: labor, environment, enforcement and prescription drug provisions, according to U.S. media.

U.S. Trade Representative Robert Lighthizer met with Pelosi and House Ways and Means Committee Chairman Richard Neal later on Thursday for further discussions, but they failed to strike a final agreement on the USMCA deal.

"Even if we could agree on the terminology, if we don't agree on the enforcement, we still have a problem," Pelosi said.

On Nov. 14, Pelosi said that a deal between House Democrats and the Trump administration over changes to the USMCA is "imminent".

The House now has only eight official session days left in the 2019 calendar year. It's not yet clear whether Congress could pass the USMCA deal during such a short time window.