Washington, Jan 5 (IANS): US President Donald Trump has said he is prepared for a partial shutdown of the US government -- now entering its third week -- to last years.

After meeting top Democrats, he also said he could declare a national emergency to bypass Congress and build a US-Mexico border wall, the BBC reported.

Trump insisted he would not sign any bill without wall funding, which Democrats adamantly oppose.

Around 800,000 federal workers have been without pay since December 22.

The Republican president initially gave a positive account of Friday's meeting at the White House, describing it as "very productive".

But then he acknowledged in response to a journalist's question that he had threatened to keep federal agencies closed for years if necessary.

"I did say that, absolutely I said that," said Trump in the executive mansion's Rose Garden. "I don't think it will but I am prepared."

"I'm very proud of doing what I'm doing," the president added. "I don't call it a shutdown, I call it doing what you have to do for the benefit and safety of our country."

When asked whether he had considered using emergency presidential powers to bypass congressional approval of funding, Trump said he had.

"I may do it. We can call a national emergency and build it very quickly. That's another way of doing it."

House Speaker Nancy Pelosi said Friday's meeting had been "contentious".

Senate Democratic leader Chuck Schumer told reporters: "We told the president we needed the government open. He resisted.

"In fact he said he'd keep the government closed for a very long period of time. Months or even years."