WASHINGTON (AFP) - Afghan President Ashraf Ghani professed deep gratitude to the American people Wednesday for their service and sacrifice in a protracted war in Afghanistan, but warned of extremism's persistent threat in a speech to US lawmakers.

Addressing a rare joint meeting of Congress one day after President Barack Obama hosted him in the White House, Ghani expressed a revitalised optimism about the US-Afghan relationship.

"We owe a profound debt to the 2,315 servicemen and women killed and the more than 20,000 who have been wounded in service to your country and ours," Ghani said, after receiving a warm welcome from members of the House of Representatives and the Senate.

Ghani presented a sharp contrast, both in style and substance, to his predecessor Hamid Karzai, whose relations with Washington grew bitter and mistrustful in his final years in office.

And, while Ghani did not mention Karzai by name, he clearly signalled a desire to turn the page after a decade of fractious ties.

The Afghan leader paused to "salute and thank" the US Congress, which controls the purse strings regarding funding for overseas operations, for its role in buttressing a nation ravaged by the Taleban and poverty.

Ghani, who took office six months ago, said Americans have provided an inspirational gift of "hope" to his nation, not only by combating extremism but in helping more than three million girls enroll in primary schools and raising the average Afghan lifespan from just 44 years in 2002 to over 60 today.

"I would like to return that gift of re-born hope by offering the American people a partnership with a nation that is committed to the cause of freedom and that will join the fight against the growing threat of terrorism."

NO 'CHARITY'

But he stressed that while Afghans appreciated the depth of American development assistance, they were intensely committed to self-sufficiency.

"We don't want your charity," he explained. "We have no more interest in perpetuating a childish dependence than you have in being saddled with a poor family member who lacks the energy and drive to go out and find a job."

And in an effort to signal that his reforms will have bite, he declared that "we will eliminate corruption" and end discrimination against women.

"There is no point talking about how much we respect women's honor if we let rape go unpunished or allow harassment in our streets," he said.

Ghani, on the first trip to Washington of his presidency, wore a dark Western-style suit, unlike Karzai, who addressed Congress in 2004 in resplendent Afghan garb.

Karzai's relationship with US officials was fraught with tension in his final years in office. He refused to sign a bilateral security agreement, a move Ghani acknowledged led to "lost momentum, and both partners had to operate under uncertainty."

But Ghani stressed that both sides "made up for the loss," with Obama able to hold to his promise of ending all US combat operations in Afghanistan by the end of 2014.

At the White House on Tuesday, the pair announced that the Pentagon will keep the current level of 9,800 US forces in Afghanistan until the end of 2015.

But Ghani sounded an ominous note to Congress, warning of the "darker cloud" of Islamic State extremism that is making its way toward Afghanistan.

"Sooner or later extremism will come knocking at our door," he said. "The world's democratic communities must unite to fight against this dangerous form of violence."

He said the Islamic State group has already begun sending "advance guards" to southern and western Afghanistan "to test for vulnerabilities," while Pakistan's counter-insurgency operations have pushed the Taleban elements towards Afghan border regions.

As for Taleban within Afghanistan, Ghani said his government will meet with the repressive group, as part of a push for national reconciliation, "from a position of strength not weakness."

Ghani was given several standing ovations in the chamber, where the mood was less tense than the controversial address Israeli Prime Minister Benjamin Netanyahu gave from the same rostrum earlier this month.

House Speaker John Boehner afterwards called Ghani a "trusted partner for peace and security," and said Congress remained committed to "securing the gains our forces have made together and completing our mission successfully."