"His bloody messages were received and are still being received by Muslims, and they will not be concealed by public relations campaigns or by farcical visits or elegant words," said an audio recording purportedly by al-Zawahiri posted on an al-Qaeda-linked website on Tuesday.
The recording could not be verified.
Robert Gibbs, the White House spokesman, said Obama's speech "will outline his personal commitment to engagement, based upon mutual interests and mutual respect".
"He will discuss how the United States and Muslim communities around the world can bridge some of the differences that have divided them."
During his brief stay in Riyadh, Obama will hold talks with King Abdullah, the Saudi monarch who has been trying to relaunch a 2002 Arab-backed regional peace initiative.
|Al-Zawahiri said Muslims would not be taken in by "farcical visits or elegant words" [AFP]
Since he took office in January, Obama has made changes to many of George Bush's policies that proved unpopular among Muslims.
He has ordered the closure of the Guantanamo Bay prison camp and set a date for the withdrawal of US combat troops from Iraq.
The US president has also called on Israel to halt the building of settlements in the occupied Palestinian West Bank.
But there has been no let up on US missile attacks on suspected al-Qaeda targets in Pakistani tribal areas and hundreds of civilians are believed to have been killed in US strikes in Afghanistan.
Marwan Bishara, Al Jazeera's senior political analyst, said Obama needed to untie himself from the idea that the Muslim world was the arena for the battle against terror.
|The US has pressed Israel to freeze settlement expansion in the occupied West Bank [AFP]
Underneath the rhetoric, it appeared that Obama was seeking to make significant changes to the US relationship with Israel, he said.
Obama said earlier on Tuesday that his country's relationship with Israel means he has to be "honest" with the country over such controversial issues as settlements and their obstruction to peace.
Obama told NPR, a US radio network, in advance of his trip to the Middle East, that he wanted to see a "new dialogue" in the region in order to forge a solution to the Middle East conflict.
"I think there have been times where we are not as honest as we should be about the fact that the current direction, the current trajectory, in the region is profoundly negative, not only for Israeli interests but also US interests," he said.
Obama also said the current situation in the region was "unsustainable" when it came to Israel's security.