Obama vows to reignite US 'engine' of growth

President Barack Obama will dare Republicans Tuesday to help build a "thriving middle class," reform immigration and curb gun crime in an ambitious State of the Union address.

Obama, wagering political chips he won in November's election, will tell Americans he will halve the number of US troops in Afghanistan within a year, and give his first on camera response to North Korea's nuclear test.

"A growing economy that creates good, middle-class jobs -- that must be the North Star that guides our efforts," Obama will say, when he lays out his second term agenda from the House of Representatives at 0200 GMT.

"It is our generation's task, then, to reignite the true engine of America's economic growth -- a rising, thriving middle class," the president will say, according to excerpts of his showpiece annual address.

Obama will promise his plans for government investment in jobs programs will not hike the deficit, and is expected to also urge Congress to act on climate change, clean energy and growing manufacturing jobs.

But Republicans, who control the House and can clog up the Democratic-run Senate, were already maneuvering to thwart Obama's second term, after losing a tussle to the president late last year over rising taxes on the rich.

Rising Republican star Marco Rubio noted in excerpts of his response to the president that the US economy shrank 0.1 percent in the last quarter of 2012, and said Obama's spending plans would make it worse.

"I hope the president will abandon his obsession with raising taxes and instead work with us to achieve real growth in our economy," Rubio said.

There is little real hope in the White House that Obama's speech will bridge toxic political divides, especially as it comes amid an ill-tempered showdown over huge budget cuts due on March 1 that could hammer the economy.

But the address, before a large television audience, will mark Obama's best chance to build support for his proposals and to delay the domestic lame duck status that eventually hobbles all second term presidents.

It will complement the soaring defense of progressive politics and equality of opportunity that anchored his inaugural address last month, and seek to find a way to turn lofty ideology into a workable legislative program.

Obama, in line with his core mission of ending a draining decade of foreign land wars, will announce the return of 34,000 of the 66,000 US troops remaining in Afghanistan by next February, ahead of a full withdrawal in 2014.

A senior Pentagon official told AFP the pullback would be tied to the fighting season in Afghanistan, which runs into the fall.

And North Korea thrust itself back into the US political debate by conducting its third nuclear test, complicating the case Obama will make for agreed cuts in the Russian and US nuclear arsenals.

Obama was likely to vow a staunch defense of US allies in Asia and called for swift and credible international action to respond to Pyongyang's provocation.

The president 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.

Another priority Obama will highlight will be 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.

An undocumented immigrant, a gay federal employee, victims of gun violence and Apple's chief executive will also be at her side, and possibly get shoutouts from the president to highlight aspects of his program.

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