WASHINGTON (REUTERS) - With the partial US government shutdown dragging into its 26th day, House Speaker Nancy Pelosi on Wednesday (Jan 16) urged President Donald Trump to reschedule his State of the Union address - a move that could deny the president the opportunity to use the pageantry of the speech to attack Democrats in their own chamber over the impasse.

With Trump's address set for Jan 29, Pelosi wrote him a letter citing security concerns because the Secret Service, which is required to provide security for the address, has not received funding during the dispute.

The standoff was triggered by Trump's demand for a round of funding for his promised wall on the US-Mexico border.

Presidents traditionally deliver the address, which lays out the administration's goals for the upcoming year, in the House of Representatives chamber before a joint session of Congress and the majority of the Cabinet.

Democrats took control of the House after last November's congressional elections. During the shutdown, Trump has routinely blamed them for the stalemate, although he had earlier said he would take responsibility.

In comments to reporters on Wednesday, Pelosi suggested that if Trump would not agree to reschedule the speech until the government reopens, he could deliver it from the Oval Office instead, a setting that would lack the grandeur of a congressional address.

The White House had no immediate comment on Pelosi's request, and her letter appeared to take aides by surprise. It pointed out that she had invited Trump to make the State of the Union address at the Capitol but said the shutdown complicated the situation.

"Sadly, given the security concerns and unless government re-opens this week, I suggest we work together to determine another suitable date after government has re-opened for this address or for you to consider delivering your State of the Union address in writing to the Congress," Pelosi wrote.

Representative Jim Jordan of the House Freedom Caucus, a group of conservative Republicans who are close allies of Trump, said Pelosi's move showed the lengths to which Democrats will go to obstruct the president.

"It sure sounds like she's looking to not have the president come and give the State of the Union address, not have the commander in chief come and address the nation," Jordan told Reuters.

"I think that just shows that they're more focused on stopping the president than they are on serving the country."

Meanwhile, both sides in the long-running conflict sought to ratcheted up the pressure.

Democratic senators huddled on the outdoor steps leading to the Senate in 3.9 deg C, windy Washington weather, holding large photographs of constituents furloughed by the shutdown or otherwise affected by it.

Senate Democratic Leader Chuck Schumer said Trump "is using these men and women as pawns. Using them in an extortion game saying, 'I am going to hurt these people unless I get my way.'"

At the same time, the president hosted a bipartisan group of House members to discuss finding a solution to the impasse.

Afterwards, White House Press Secretary Sarah Sanders called the meeting "constructive."

A handful of Republican senators, including Lindsey Graham and Lisa Murkowski, circulated a bipartisan draft letter to Trump asking him to support a measure that would reopen the government for three weeks while they work on funding legislation that would address his concerns about border security.

A Democrat who signed the letter, Chris Coons, said the letter would not be sent unless a substantial amount of Republicans supported it.

Trump on Wednesday is expected to sign legislation that would ensure 800,000 federal employees will receive back pay when the government reopens.

Some government employees are being asked to return to work after being initially told to stay home during the shutdown, although they will not be paid on schedule.

Both the Internal Revenue Service and the Federal Aviation Administration on Tuesday said they would call back nearly 50,000 employees to handle tax returns, refunds and other tasks or to work in aviation safety inspection.

The US Department of Agriculture said it was recalling about 2,500 furloughed Farm Service Administration employees to assist farmers with existing loans and ensure the agency meets a deadline for providing tax documents.

The Washington Post reported that Food and Drug Administration workers also have been called to work without pay during the shutdown.

The shutdown began on Dec 22 after Trump insisted he would not sign legislation funding the idled government agencies unless it included more than US$5 billion (S$7 billion) for the border wall.

The wall was a signature campaign promise of his before the 2016 presidential election. Trump said at the time Mexico would pay for it but has since reversed himself, denying that he ever said Mexico would directly pay the bill.