By Doina Chiacu

WASHINGTON, Jan 13 (Reuters) - A Republican senator close to President Donald Trump on Sunday backed a temporary re-opening of the federal government, in the 23rd day of the longest shutdown ever, to allow for talks on a spending agreement that could satisfy Trump's border security demands.

Democrats in Congress rejected Trump's request that legislation to fund the government include $5.7 billion of taxpayer money for a wall on the U.S. border with Mexico. They have refused further negotiations until the government is reopened after being partially shut down since Dec. 22.

Graham, chairman of the Senate Judiciary Committee, said he urged the president on Sunday to reopen the government for a limited period to try to get talks going again.

If no progress is made, he said, then Trump should declare a national emergency as a way to get money to build his wall, a plan not popular with some fellow Republicans.

"Before he pulls the plug on the legislative option, and I think we are almost there, I would urge them to open up the government for a short period of time, like three weeks, before he pulls the plug (to) see if we can get a deal," Graham said on the "Fox News Sunday" program.

He said Trump told him, "Let's make a deal, then open up the government."

The record shutdown has furloughed 800,000 federal employees and cut government services across the United States. They missed their first paychecks on Friday, heightening concerns about mounting financial pressures on employees, including air traffic controllers and airport security officials who are working without pay.

Trump continued to blame Democrats for the impasse. "I'm in the White House, waiting. The Democrats are everywhere but Washington as people await their pay. They are having fun and not even talking!" Trump said Sunday on Twitter.

However, Trump said last month he would be "proud" to shut down the government over wall funding and recent polls show most Americans think the president is to blame.

Jennifer Lawless, a politics professor at the University of Virginia, said she believes Trump and Republicans will lose the game of chicken as furloughed workers, airport travelers, tourists and others "experience the consequences of political dysfunction firsthand."

"The shutdown is real. The wall is hypothetical. And at some point soon, the Republicans are going to remember that it's real people in their districts who aren't getting paid, real people who aren't able to access government services, and real people who vote," she said.

A concourse at Miami International Airport was shut down for part of the weekend because not enough Transportation Security Administration agents were present to staff all of the airport's the security checkpoints.

The airport said it would reopen the concourse on Monday and "continue to monitor checkpoint staffing levels and make adjustments as necessary."

Working without pay, TSA employees have been calling in sick in increasing numbers since the shutdown began. On Sunday, TSA said it had a 7.7 percent national rate in unscheduled absences, compared with 5.6 percent on Saturday and 3.2 percent a year ago.

Democrats hammered away at their demand that Trump reopen the government. Senator Tim Kaine called the wall, which could cost an estimated $23 billion, a "vanity project" that Trump promised Mexico - not U.S. taxpayers - would pay for.

"Put an end to the shutdown and put everything on the table," Dick Durbin, the No. 2 Democrat in the Senate, said on ABC's "This Week" show.

Trump campaigned against illegal immigration in 2016 and said a wall is necessary to keep illegal immigrants from entering the country. (Reporting by Doina Chiacu; Additional reporting by David Shepardson and Sarah Lynch in Washington, and Gabriella Borter in New York; Editing by Jeffrey Benkoe)

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