WASHINGTON (AFP) - President Barack Obama on Friday branded the automatic budget cuts about to slam into the US economy as "dumb" and "unnecessary" but blamed Republicans for the failure to avert them.

"These cuts will hurt our economy, will cost us jobs and to set it right both sides need to be able to compromise," Mr Obama said, on the day US$85 billion (S$105 billion) in cuts go into force after lawmakers failed to reach a deficit-cutting deal.

"I am not a dictator. I am a president," Mr Obama said, after a last-minute meeting with top congressional leaders failed to broker a deal to prevent the arbitrary and automatic cuts, known as sequestration, from coming into force.

"What I can't do is force Congress to do the right thing," Mr Obama said.

"In the absence of a decision on the part of the Speaker of the House and others to put middle class families ahead of whatever political imperatives he might have right now, we are going to have these cuts in place."

Mr Obama welcomed his chief foes, House Speaker John Boehner and Senate Republican minority leader Mitch McConnell to the Oval Office, along with Democratic Senate chief Harry Read and top House Democrat Nancy Pelosi.

Mr Boehner emerged from the talks with the president to tersely signal to reporters that Republicans would not budge on Mr Obama's key demand for a deal which would raise tax revenues.

"Let's make it clear that the president got his tax hikes on Jan 1. This discussion about revenue in my view is over," Mr Boehner said.

"It is about taking on the spending problem in Washington."

Mr Obama was bound by law to initiate the automatic, indiscriminate cuts, which could wound the already fragile economy, cost a million jobs and harm military readiness, by 11.59 pm local time in the absence of an deficit cutting agreement.

The hit to military and domestic spending, known as the sequester, was never supposed to happen, but was rather a device seen as so punishing that rival lawmakers would be forced to find a better compromise to cut the deficit.

But such is the dysfunction in gridlocked Washington that neither side tried very hard to get a deal, with Mr Obama calling for tax revenue hikes on the wealthy and corporations - a demand Republicans flatly refused.

The drama instead evolved into the latest philosophical standoff over the size, role and financing of government between Mr Obama, who won re-election vowing to protect the middle class, and fiscally conservative Republicans.

Mr Obama, in effect extending the campaign that won him re-election in November, has mounted a fierce public relations offensive designed to maximise his leverage by pouring blame on Republicans for the cuts.

"Instead of closing a single tax loophole that benefits the well-off and well-connected, (Republicans) chose to cut vital services for children, seniors, our men and women in uniform and their families," Mr Obama said on Thursday.

"They voted to let the entire burden of deficit reduction fall squarely on the middle class."

Republicans accuse Mr Obama of inflating the impact of the sequester and of using scare tactics and believe he has painted himself into a political corner.

The White House admits it will take time for the full impact of the sequester to be felt, as government workers get furlough notices and services, like education for special needs kids, are put at risk.

But it said the results of the cuts would nevertheless be emphatic.

Although the cuts trim significant amounts from domestic and defence spending, they do not touch entitlements - social programmes like Medicare health care for the elderly and pension schemes.

Many budget experts believe that only cuts to those programs will be able to restore the prospect of long-term fiscal stability.

The White House warns that the indiscriminate cuts are written into law in such a way that their impact cannot be alleviated.

It says 800,000 civilian employees of the Defence Department will go on a mandatory furlough one day a week and the navy will trim voyages. The deployment of a second aircraft carrier to the Gulf has been canceled.

About 70,000 children less than five years old will be cut from the Head Start preschool programme, resulting in the elimination of 14,000 teaching positions. Services for special needs kids will also take a hit.

Authorities warn that average wait times for passengers at US immigration will increase by 30 to 50 per cent and may exceed four hours during peak times.