The second-in-command of Islamic militant network al-Qaeda has called on Muslims to harm "criminal" America. In a message purportedly from Ayman al-Zawahiri, the al-Qaeda deputy accused US President-elect Barack Obama of betraying his Muslim roots.
He likened him to a "house slave" - who had chosen to align himself with the "enemies" of Islam.
Mr Obama has said stamping out al-Qaeda "once and for all" will be a top priority during his administration.
On Sunday, he said capturing or killing Osama Bin Laden was "critical" to US security.
He has also promised to bolster the US presence in Afghanistan - a policy that would fail, said the al-Qaeda deputy.
The US said the message did not signal any increased threat against America.
This is undoubtedly a message aimed at sustaining anti-American sentiment among Muslims in the face of Barack Obama's election, says the BBC's defence correspondent Rob Watson.
But it is a risky approach, our correspondent says.
Barack Obama is hugely popular world-wide and his colour and background make him a much tougher target to attack than President George W Bush in the eyes of a global audience, he says.
Zawahiri, an Egyptian by birth, is often referred to as Osama Bin Laden's right-hand man and the chief ideologue of al-Qaeda.
The audio message, which ran with photographic stills and some video footage, appeared on militant websites.
Mr Obama's election did not mean that US policy towards the Muslim world had changed, Ayman al-Zawahiri said, according to the 11-minute message.
He warned Mr Obama of failure if he followed the policies of the Bush administration.
The change of leadership in the US did not mean that America should be perceived differently, he added.
"America, the criminal, trespassing crusader, continues to be the same as ever, so we must continue to harm it in order for it to come to its senses," he said.
Zawahiri also criticised Mr Obama - whose father is Muslim - for betraying the Islamic world.
"You were born to a Muslim father, but you chose to stand in the ranks of the enemies of the Muslims, and pray the prayer of the Jews, although you claim to be Christian, in order to climb the rungs of leadership in America," he said.
Mr Obama was not an "honourable black American" like Malcolm X, he said, but an "abeed al-beit" - a word that translates as house slave but was rendered "house negro" in the message's English subtitles.
The audio was accompanied by footage of a speech by Malcolm X in which he distinguished between "field negroes" who hated their white masters and "house negroes" who, he said, were loyal to them.
US State Department spokesman Sean McCormack described the message as "more despicable comments from a terrorist".
Mr Obama visited Israel in July and expressed his "abiding commitment" to its security.
On Sunday, in his first television interview since his 4 November election win, he reiterated his commitment to shift more US troops to bolster the military presence in Afghanistan.
The last message purporting to be from Zawahiri emerged on 8 September. He is thought to be in hiding in the Afghan-Pakistan border area.