President Donald Trump said on Friday he has reached a tentative agreement with U.S. lawmakers for three weeks in stop-gap funding that would end a partial U.S. government shutdown now in its 35th day, with a senior Democratic aide saying money the president demanded for a border wall is not included.

The president had previously insisted on the inclusion of US$5.7 billion to help pay for a wall along the vast U.S.-Mexico border in any legislation to fund government agencies.

"I am very proud to announce today that we have reached a deal to end the shutdown and reopen the federal government," Trump said in remarks in the White House Rose Garden.

"In a short while, I will sign a bill to open our government for three weeks until Feb. 15. I will make sure that all employees receive their back pay very quickly, or as soon as possible," Trump said.

With the effects of the shutdown spreading on Friday, Trump said a bipartisan congressional conference committee would meet to come up with a plan for border security.

Trump triggered the shutdown, which began on Dec. 22 and idled some 800,000 government employees, with his wall-funding demand but Democrats, who control the House of Representatives, rejected it on the grounds that a wall would be costly, ineffective and immoral. Trump, whose Republicans have a majority in the Senate, has said it is necessary to curb illegal immigration and drug trafficking.

The arrangement, which would require passage in the House and Senate and Trump's signature, would leave his request for wall funding for later talks, a House Democratic aide said. The House could pass the measure as soon as later Friday if Republicans agree to hold a vote, the aide said.

A Senate Republican aide said Senate Majority Leader Mitch McConnell was expected to press for passage of a three-week funding bill on Friday.

"We do not need 2,000 miles of concrete wall from sea to shining sea. We never did," Trump said. "We never proposed that. We never wanted that because we have barriers at the border where natural structures are as good as anything that we could build.

"Our proposed structures will be in predetermined, high-risk locations that have been specifically identified by the Border Patrol to stop illicit flows of people and drugs," Trump said.

The temporary funding bill would extend agency funding at the last fiscal year's levels and would include some money for border security - but not a wall.

Democratic Senator Patrick Leahy, a senior member of the Senate Appropriations Committee, said he wanted to hear what Trump had to say before he would assume there was an iron-clad deal.

In one of the many effects of the shutdown, hundreds of flights were grounded or delayed at airports in the New York area and Philadelphia on Friday as more air traffic controllers called in sick.

The Federal Aviation Administration issued a ground stop for flights destined for New York's LaGuardia Airport on Friday morning before lifting it about an hour later. Staff shortages also delayed flights at Newark Liberty International Airport and Philadelphia International Airport, the FAA said.

Hundreds of thousands of federal workers have been furloughed or, as with some airport workers, required to work without pay. Some federal agencies have reported much higher absence rates among workers as they face an indefinite wait for their next paychecks.

The lapse in funding has shuttered about one-quarter of federal agencies, with about 800,000 workers either furloughed or required to work without pay. It is the longest such shutdown in U.S. history. Many employees as well as contractors were turning to unemployment assistance, food banks and other support. Others began seeking new jobs.

Democratic House Speaker Nancy Pelosi told reporters on Thursday the possibility of legislation that includes a large down payment on a wall, "is not a reasonable agreement."