The Obama administration is pressing Congress to raise the government's debt limit, a typically routine request that this year promises to be considerably less so as it highlights perhaps the biggest threat facing the U.S. economy.

For decades, presidents have asked Congress to raise a debt limit first imposed during the First World War. Sometimes, lawmakers put up a fight, but ultimately they acquiesce. America’s creditworthiness is on the line.

But the U.S.’s peacetime debt burden has never been this heavy. That made U.S. Treasury Secretary Timothy Geithner’s request to Congress on Thursday to lift the current $14.4-trillion (U.S.) debt ceiling more than routine, especially since several members of the new Republican majority in the House of Representatives have already said they intend to say “no.”

“A lot of Americans are genuinely concerned about the national debt, even if they do not really understand what is needed to reduce it,” said Joseph Gagnon, a former Treasury official who is now a senior fellow at the Peterson Institute for International Economics in Washington. “So raising the debt ceiling has symbolic importance.”

The U.S. deficit in the fiscal year that ended Sept. 30 was $1.3-trillion. Federal spending amounted to 24 per cent of gross domestic product, the most since the Second World War. The country’s debt has risen to 62 per cent of GDP from 33 per cent in 2001.

A bipartisan commission set up by President Barack Obama last year to propose ways to reduce the deficit failed to come up with a compromise.

Yields on U.S. Treasuries have been rising lately, in part because some investors are starting to question whether the U.S. political system is up to the challenge of narrowing the deficit, analysts say.

“It’s different this time,” said Andrew Busch, global currency and public policy strategist at BMO Nesbitt Burns in Chicago. “The stakes are larger.”

In a letter sent to all members of the House of Representatives and Senate, Mr. Geithner told lawmakers that he has about $335-billion of “headroom” before the demands of financing the budget deficit force him up against the debt ceiling.

The White House is trying to get ahead of the new Republican majority in the House, which elected Ohio’s John Boehner as speaker on Wednesday. Some newly elected Republicans, who won election on promises to dramatically cut spending, have said in recent weeks that they would vote against increasing the debt limit. Mr. Geithner’s intervention shows the Obama administration will try to counter the Republican rhetoric about the debt with a challenge to govern responsibly.

Based on the Treasury’s current revenue and spending estimates, the debt limit could be reached as early as March 31, and at the latest by the middle of May, Mr. Geithner said. Rather than wait for the last minute, the Treasury Secretary asked lawmakers to increase the debt ceiling by the end of the first quarter.

Without a change, the Treasury would be blocked by law from issuing bills and bonds to fund government operations. That would include paying interest on existing debt obligations, which would amount to default. The U.S. has never missed a debt payment in its history. To do so likely would result in higher borrowing costs, which would have a ripple effect through the economy because Treasuries act as benchmarks for consumer and corporate borrowing rates.

“Even a very short-term or limited default would have catastrophic economic consequences that would last for decades,” Mr. Geithner wrote, predicting it would result in the loss of “millions” of jobs. “Failure to increase the limit would be deeply irresponsible,” he said.

Congress first restrained the executive’s ability to borrow in 1917, when the administration of Woodrow Wilson sought approval to issue bonds to finance the U.S. entry into the First World War. The debt ceiling has been routinely raised ever since, including about 70 times since the early 1960s, according to a study by the Congressional Research Service.

But routine doesn’t always mean easy. When the parties in power in the White House and Congress misalign, the vote on the debt ceiling usually sees one side accusing the other of fiscal mismanagement. In the past, the game of chicken between the administration and Congress has forced the Treasury to take extraordinary delaying tactics, such as suspending the issue of certain securities.

“Treasury would prefer not to have to engage again in any of these extraordinary measures,” Mr. Geithner said.

Mr. Boehner said in a statement that the U.S. can afford neither default nor “recklessly” continuing to borrow. “The American people will not stand for such an increase unless it is accompanied by meaningful action by the President and Congress to cut spending and end the job-killing spending binge in Washington,” Mr. Boehner said.

A Treasury official, who spoke to reporters in Washington on the condition of anonymity, said the administration intends to significantly reduce the deficit, but believes the debt limit should be raised without linking it to changes in fiscal policy, according to a report by Bloomberg News. The official said the Obama administration believes lawmakers will vote to increase the debt ceiling.

For now, most investors will assume Mr. Obama and Mr. Boehner take their dance down to the wire, and then find a resolution to avoid the worst, said Mr. Busch. He predicted the Republicans would agree to lift the debt ceiling on a month-by-month basis to keep the issue fresh in voters’ minds.

“The Republicans aren’t going to shut down the government, but they aren’t going to make it easy for the administration,” Mr. Busch said.