A group of bipartisan and bicameral lawmakers, dubbing themselves the "908 Coalition," signed a public letter on Sunday, urging President Trump to sign a much-needed COVID-19 emergency relief package or "veto it immediately."

The letter, signed by eight U.S. Senators and two U.S. House members, comes after the president blindsided members of both parties with a demand for larger COVID relief checks, imperiling not only a massive package of economic and public-health assistance but the basic functions of government itself.

FILE: President Donald Trump walks on the South Lawn of the White House in Washington before boarding Marine One.  (AP)

"Mr. President, we are asking you to please sign the emergency relief bill," read the letter from the "908 Coalition," named after the $908 billion coronavirus package. "This act will show your support for the American people who are in need of emergency lifelines like food, shelter, unemployment benefits and small business relief during these challenging times."

The coalition urged President Trump to formally veto the bill if he objects to it. Doing so, they say, will make his position clear, and "rejecting it quickly will allow those in favor to act before it is too late."

"Never before in your personal, professional, or political life have you been characterized as a man of inaction. Now is not the time to sit idly by – please do the right thing and sign or veto this bill immediately."

Later Sunday, President Trump tweeted that he had some "good news" pending on the COVID relief bill. 

The COVID relief package passed with wide margins in the House and Senate and with the understanding of members of both parties that Trump supported it. The federal government will run out of money at 12:01 a.m. on Tuesday if Trump refuses to sign the bill before as he spends the holidays in Florida.

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Trump has given no indication he plans to sign the bill as he spends the last days of his presidency in a rage. His dissatisfaction with the legislation seems only to have grown in recent days as he has criticized it both privately to club members and publicly on Twitter.

Democrats said they would call House lawmakers back to Washington for a vote Monday on Trump's proposal to send out $2,000 relief checks, instead of the $600 approved by Congress. The idea is likely to die in the Republican-controlled Senate. Democrats were also considering a vote Monday on a stop-gap measure aimed at keeping the government running until President-elect Joe Biden is inaugurated Jan. 20.

Washington has been reeling since Trump turned on the deal, without warning, after it had won sweeping approval in both houses of Congress and after the White House had assured Republican leaders that Trump would support it.

Instead, he assailed the bill's plan to provide $600 COVID relief checks to most Americans — insisting it should be $2,000. House Republicans swiftly rejected that idea during a rare Christmas Eve session. But Trump has not been swayed despite the pandemic gripping the nation.

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The relief was attached to a $1.4 trillion government funding bill to keep the federal government operating through September, which would mean that failing to sign it by Tuesday would trigger a federal shutdown.

The Associated Press contributed to this report.