LONDON, Dec. 31 (Xinhua) -- U.S. ambassador to UK Woody Johnson on Monday warned that his country's offer of a quick bilateral trade deal with Britain would not be possible if Brexit agreement is approved.

The comment came ahead of the parliament vote of the Brexit deal agreed by the British government and the European Union (EU).

Ambassador Johnson told local media that Britain was in need of leadership over Brexit, saying MPs felt frustrated by "trying to navigate what the people wanted when they voted" to leave the EU.

Johnson said there was still hope for a UK-US trade deal, adding "We're still going through the stages of deciding exactly where the country is going."

"What I'm focusing on here is something the president has also said - that is looking forward to, and hoping, that the environment will lead to the ability for the U.S. to do a quick, very massive bilateral trade deal," he said.

Asked if that would go ahead under the current proposed Brexit deal, he replied: "It doesn't look like it would be possible."

He said ministers had to "measure the impact of all the other trade offs" and how different trade agreements would benefit Britain.