The majority of the 50-minute tape attributed to Gadahn is in English, although the call to attack the US president is made in Arabic.

"I send this urgent call to our brothers the Mujihidin, mainly in Palestine and the Arabian Peninsula, and in the region in general, to be ready to welcome the crusader, the butcher Bush," he said, according to a translation.

Bush visit

Bush is due to arrive in Israel on Wednesday, the first US president to visit the state in nine years, in an attempt to encourage the peace negotiation renewed at a conference in Annapolis last year.

He is also due to visit the West Bank and five Arab states.

"The jihad against you will remain our duty as long as there remains even one Muslim in American captivity"

Adam Gadahn, American al-Qaeda member
Gadahn's message strongly criticises Hosni Mubarak, Egypt's president, and Saudi Arabia's King Abdullah who will welcome Bush to their countries as part of the eight-day tour of the region.

It also contained an attack on Pervez Musharraf, Pakistan's president, for his support of the United States.

Gadahn, also known as Azzam al-Amriki or Azzam the American, said that the "jihad" against the US would continue until it released Muslims from its jails.

In the video he took his US passport from his breast pocket and showed its pages to the camera before ripping it up in protest at the treatment of Muslim detainees.

"The jihad against you will remain our duty as long as there remains even one Muslim in American captivity," he said.

"That is why it is incumbent upon you [the American people] to take the steps necessary to force the regime in Washington to free each and every one of them, wherever they are and whatever their supposed crime."

Treason charges

In October 2006, California-born Gadahn became the first person to be charged in the US with treason since the second world war.
The charge carries a minimum of five years in prison on conviction and a maximum penalty of death.

He is believed to be living in Pakistan and a $1m reward has been offered for his capture. He appears, along with Osama bin Laden on a US "wanted" poster featuring 26 "faces of global terrorism".

Gadahn converted to Islam from a Jewish-Christian family when he was 17 and a few years later moved to Pakistan.