A letter from the deputy of Osama bin Laden to an insurgent leader in Iraq warns against repeating the mistakes of Afghanistan's ousted Taliban movement and calls for development of a political base in preparation for the eventual "exit of the Americans," according to a copy released today by U.S. intelligence.

The 13-page English translation of the letter from Ayman Zawahiri, an Egyptian doctor and No. 2 man in the al Qaeda terrorist network, was released today by the Office of the Director of National Intelligence. It is dated July 9 and was captured recently "during counterterrorism operations in Iraq," the office said in a statement.

U.S. intelligence officials believe the letter was written to Abu Musab Zarqawi, a Jordanian terrorist who heads an al Qaeda-affiliated organization in Iraq. However, a couple of passages indicate that it may be addressed to another person in Zarqawi's organization.

In the letter, Zawahiri, who uses the alias "Abu Muhammad," outlines a four-stage plan to establish an Islamic "caliphate" that covers as much of Iraq as possible. "The first stage: Expel the Americans from Iraq," the letter says. The next stages are to establish an Islamic authority, or emirate, on Iraqi territory and to "extend the jihad wave to the secular countries neighboring Iraq." The fourth stage, it says, is "the clash with Israel, because Israel was established only to challenge any new Islamic entity."

Zawahiri describes as inevitable the departure of U.S. forces from Iraq and urges the insurgents to prepare for it. "This may develop faster than we imagine," he writes. "The aftermath of the collapse of American power in Vietnam -- and how they ran and left their agents -- is noteworthy. Because of that, we must be ready starting now, before events overtake us."

He adds, "We don't want to repeat the mistake of the Taliban," who he says governed narrowly and "did not have any representation for the Afghan people in their ruling regime."

In a statement accompanying the release of the letter, the Office of the Director of National Intelligence said the U.S. government "has the highest confidence in the letter's authenticity." It said the document, posted on the office's Web site in both English and the original Arabic, "has not been edited in any way and is released in its entirety."

The statement said the letter shows the "isolation and dependence" of al Qaeda's senior leadership. It also said the letter acknowledges "the appeal of democracy to the Iraqis."

Zawahiri warns in the letter that insurgents in Iraq "must not have their mission end with the expulsion of the Americans from Iraq, and then lay down their weapons, and silence the fighting zeal." He adds, "Instead, their ongoing mission is to establish an Islamic state, and defend it, and for every generation to hand over the banner to the one after it until the Hour of Resurrection."

In waging the insurgency, the movement must pay closer attention to gaining popular support, Zawahiri says.

"In the absence of this popular support, the Islamic mujahed movement would be crushed in the shadows," he writes. He stresses "the need to direct the political action equally with the military action, by the alliance, cooperation and gathering of all leaders of opinion and influence in the Iraqi arena."

In particular, Zawahiri advises against highlighting "doctrinal differences" among Muslim sects, attacking rival Muslim clerics and carrying out videotaped beheadings of hostages.

He also has words of caution about the Zarqawi group's war against Iraq's majority Shiite Muslims, despite his agreement that Shiites "cooperated with [the Americans] in the overthrow of Saddam [Hussein] and the occupation of Iraq" in exchange for assuming power.

"Many of your Muslim admirers amongst the common folk are wondering about your attacks" on the Shiites, the letter says. It expresses special concern about attacks on Shiite mosques and on "ordinary" Shiites.

Besides, Zawahiri asks, "can the mujahedeen kill all of the Shia in Iraq? Has any Islamic state in history ever tried that?"

He also urges the insurgents not to forget that neighboring Shiite-ruled Iran holds more than 100 al Qaeda prisoners, "many of whom are from the leadership who are wanted in their countries."

Regarding "scenes of slaughtering the hostages," a reference to beheadings that have been videotaped and shown on Internet sites, Zawahiri says, "You shouldn't be deceived by the praise of some of the zealous young men and their description of you as the shaykh of the slaughterers, etc."

The letter provides a few personal details of Zawahiri, 54, the founder of Egyptian Islamic Jihad and a man wanted by the United States for his alleged role in the 1998 bombings of U.S. embassies in Africa, among other terrorist acts.

He says he is "in good health" and recently fathered a daughter named Nawwar. But he also says he has personally "tasted the bitterness of American brutality." He says his "favorite wife" was killed when her chest was crushed by a concrete ceiling, apparently the result of an attack. He writes that his daughter died of a brain injury, and he refers to the deaths of a son and "three other families who were martyred in the incident." He says he does not know where any of them are buried.

"However, despite all of this, I say to you: that we are in a battle, and that more than half of this battle is taking place in the battlefield of the media," the letter says. "And that we are in a media battle in a race for the hearts and minds of our Umma," or community of Muslims.