North Korea's nuclear blast Tuesday rudely interrupted President Barack Obama's rollout of his State of the Union address, which is billed as a catalyst for a second-term drive to create jobs.

Obama was also to tell war-weary Americans he will bring 34,000 more troops home from Afghanistan within a year, as he winds up a more than a decade of foreign overstretch and tries to restore middle class security at home.

Less than a month into his second term, the president will step up to deliver the annual showpiece speech in the House of Representatives -- and before a huge national television audience -- at 9:00 pm (0200 GMT).

Obama will strike the populist message that helped him defy tough times to win re-election in an address largely aimed at a domestic audience -- in a down payment from the stock of political capital he piled up in November.

But North Korea's test presents him with a new foreign policy headache in Asia, as Pyongyang shrugs off sanctions which have kept it in deep isolation to stride closer to full membership of the nuclear club.

Obama had already been under fire from political opponents over another nuclear imbroglio, with Iran, as he argues for more time for punishing sanctions to convince the Islamic Republic to halt its atomic development.

Ironically, Obama had been expected to renew his core commitment to seek cuts in global nuclear weapons stocks, which has been at the core of his foreign policy, during his speech on Tuesday.

In his speech, Obama will likely mirror his middle-of-the-night statement in which he slammed the North Korean blast as "provocative" and demanding a swift and credible international response.

It did not take long for Republicans to seek to exploit the test to dent Obama's foreign policy credentials.

Howard "Buck" McKeon, Republican chairman of the House Armed Services committee, said the test proved that cuts to the US nuclear arsenal could endanger American national security.

"It is also unfortunate that on the same day the President of the United States plans to announce further reductions in US nuclear weapons, we see another hostile regime unimpressed by his example," McKeon said.

North Korea's action once again revealed Pyongyang's penchant for using big events, like major Obama speeches or a current transfer of political power in South Korea, to issue a flamboyant demand for attention.

It also came as Obama nominees Chuck Hagel and John Brennan await confirmation votes to be the next chiefs of the Pentagon and Central Intelligence Agency, after encountering opposition from Republicans.

Obama will also announce on Tuesday that he will effectively halve the 66,000-strong US garrison in Afghanistan and bring home 34,000 troops within the next year, ahead of a full withdrawal in 2014.

The president will still likely use the bulk of the State of the Union speech to lay out a governing program to match the soaring progressive vision of his inaugural address last month.

"The President has always viewed the two speeches, the inaugural address and the State of the Union, as two acts in the same play," White House spokesman Jay Carney said, before word came of the North Korean nuclear test.

"The core emphasis that he has always placed in these big speeches remains the same and will remain the same, which is the need to make the economy work for the middle class."

But the speech will take place in the shadow of Obama's row with Republicans over huge budget cuts due to hit in March 1, which could hammer the economy.

There are new reasons for alarm over the flat economy, after GDP contracted at an annual rate of 0.1 percent in the last quarter of 2012 and the unemployment rate ticked up to 7.9 percent.

The White House argues, however, that there is no comparison between the howling crisis that Obama inherited four years ago and the economy of today, although it does not dispute that many Americans are still hurting.

While jobs will be his prime focus, Obama is also likely to highlight other domestic issues, though he knows Washington's bitterly partisan climate could render many big plans dead on arrival on Capitol Hill.

One priority will be building support for new laws to curb gun violence, after the horror of December's massacre of 20 small kids at a school in Newtown, Connecticut.

First Lady Michelle Obama will host in her House box the parents of Hadiya Pendleton, a teenager gunned down in a random shooting not far from the president's Chicago home days after she took part in his inaugural parade.

Aides said Obama will pitch immigration reform, the centerpiece of his second-term agenda, amid signs that Republicans keen to mend fences with Hispanic voters may be ready for some rare cross-party compromise.