LONDON, Dec. 9 (Xinhua) -- British Prime Minister Theresa May on Sunday warned lawmakers against voting down her deal, saying there would be "uncharted waters" ahead.

The warning came two days ahead of a crucial Brexit vote in the House of Commons.

Speaking to the Mail on Sunday, May said a rejection of her proposals would mean "grave uncertainty" for her country.

"When I say if this deal does not pass we would truly be in uncharted waters, I hope people understand this is what I genuinely believe and fear could happen," she was quoted as saying.

She warned members of parliament (MPs) their actions could lead to a "very real risk of no Brexit" and also a general election.

The prime minister's office denied that May could postpone the vote where dozens of Conservative MPs are expected to vote against the deal.

Opposition parties, including Labor, the Liberal Democrats and the Scottish National Party, have said they cannot support the deal.

The Brexit deal, reached by Britain and the European Union, needs the approval of the British parliament.

If the deal is rejected, what happens next remains unclear.

Brexit Secretary Steve Barclay told the Sunday Telegraph the government is "preparing for all scenarios."

"The choice is this deal, no deal, or no Brexit at all -- with this deal by far the best outcome," he said.