WASHINGTON (AP) — House Democrats say President Barack Obama should consider invoking a little-known constitutional provision that they say gives him the power to raise the debt ceiling without going through Congress, where Republicans are demanding that a debt ceiling vote be linked to spending cuts.

The Democrats said in a letter that they would support the use of any authority, including the 14th Amendment, to prevent the nation from going into default, an event that some economists predict could trigger a global recession.

That post-Civil War amendment contains a section stating that "the validity of the public debt of the United States...shall not be questioned."

As of Wednesday 21 Democrats, led by Rep. Peter Welch of Vermont, had signed the letter.

Raising the federal borrowing limit is now subject to congressional approval, which traditionally has come with relatively little resistance. But in July 2011 Republicans tied their vote on the debt ceiling to concessions on spending, generating a confrontation with the Obama administration and resulting in the first-ever ratings downgrade of the nation's credit-worthiness.

The government faces a similar crisis now because the $16.4 trillion borrowing limit has been reached and by late February or early March the Treasury Department will run out of ways to cover debts and could begin defaulting on government loans.

Both in 2011 and again this year the White House has shown little interest in trying an end-run around Congress. "This administration does not believe the 14th Amendment gives the president the power to ignore the debt ceiling," White House spokesman Jay Carney said last month.

There is no legal precedent for applying the 14th Amendment to circumvent a congressional vote and such an action would be certain to result in legal challenges.

The Democrats, in their letter, said they fully supported Obama's position that raising the debt ceiling will not be subject to negotiation. "Threatening default on our nation's debt is an economic weapon of mass destruction that will have immediate and catastrophic consequences for the economy as well as America's standing in the world," they said.

Welch, in an interview, told The Associated Press said he understood that the president might not want to embrace the 14th Amendment alternative at this point, when it might appear to be a power grab. But "if there is the ultimate act of congressional irresponsibility by having the United States default on its obligations, we encourage the president to rescue the country." He said ultimately the courts would have to decide what authority the amendment confers on the president.