An audiotape allegedly recorded by a Jordanian-born al-Qaeda suspect, Abu Musab al-Zarqawi, has threatened attacks on US commanders in Iraq.
The tape's authenticity has not yet been verified
The tape - aired on an Islamist website - also claimed responsibility for a number of high-profile attacks there.
Zarqawi's whereabouts are unknown, but the website had a transcript heading that said he was in Iraq.
Washington has accused the 38-year-old of masterminding a string of suicide bombings in Iraq.
On Tuesday, Zarqawi was one of eight Islamic militants to be sentenced to death by a Jordanian court for killing a US government official, Laurence Foley, in Amman in October 2002.
The speaker singled out the overall commander of US forces in Iraq and the Middle East, General John Abizaid, and the top US administrator in Iraq, Paul Bremer, for attacks.
"If John Abizaid escaped our swords this time, we will be lying in wait for him, for Bremer, for their generals and soldiers, and their collaborators."
He also took credit for several attacks, saying "the most recent and not the last was against the Israeli Mossad in the Mount Lebanon hotel."
A car bomb explosion in front of that hotel on 17 March killed seven and wounded a dozen people.
"We challenge the dishonest US media to reveal the real damage and big losses sustained by their forces... There will be more rounds of fighting, God willing."
The tape also urged militants to target Iraq's majority Shias and "burn the earth under the occupiers' feet".
The speaker said the Shia were not true Muslims and were "the ears and the eyes of the Americans" in Iraq.
This theme echoed a letter - released by the Americans in February 2004 - purported to be from Zarqawi to al-Qaeda leaders.
In it, the author appeared to share his plans for igniting sectarian conflict in Iraq as a means of undermining the US presence there.