A previously secret document found at Osama bin Laden's compound in Pakistan sets out a detailed al-Qaida strategy for attacking targets in Europe and the United States.

The document -- a letter written to bin Laden in March 2010 by a senior operational figure in the terror group -- reveals that tunnels, bridges, dams, undersea pipelines and Internet cables were among the targets.

It was written by Younis al-Mauretani, a senior al-Qaida planner thought to have been behind an ambitious plan to hit "soft" targets in Europe in the fall of 2010.

The U.S. Department of Justice passed the letter to German prosecutors last year for use in an ongoing trial in Dusseldorf because it possibly refers to one of the defendants, according to the German newspaper Die Zeit, which first broke the story.

CNN has obtained details of the document from sources briefed on its contents. The 17-page letter is in Arabic.

Al-Mauretani proposed that al-Qaida recruits take jobs with companies transporting gasoline and and other sensitive companies in the West, and await the right moment to strike.

He said targets should include tunnels, airports and even "Love Parades" -- gay and lesbian events held every summer in Germany. He said recruits should infiltrate university courses in the West in key subjects useful to the group including physics and chemistry, so that they could later be re-activated and help the group, according to Die Zeit.

He also suggested attaching mines to undersea pipelines using mini-submarines -- and appears to have researched ways to circumvent safety valves on such pipelines. Al Mauretani also proposed that al-Qaida attack financial centers and think-tanks -- specifically mentioning the RAND Corporation, whose headquarters are in California.

Asked if it was aware of the threat, a spokesman for RAND told CNN that "as a matter of policy, the RAND Corporation does not comment on specific security issues or potential threats."

Yassin Musharbash, an investigative reporter with Die Zeit in Berlin, says the document seems "to support information gleaned from other terror trials that al-Qaida in 2010 was trying to plan a comprehensive plot against the West," and al-Mauretani appears to have been bent on "hitting Europe and the U.S. by targeting critical infrastructure and economic targets."

Some of al-Mauretani's ideas may seem far-fetched, but they underline al-Qaida's continuing fascination with bringing down airliners. He proposed that men recruited into the Yemeni al Qaeda affiliate AQAP become pilots with airlines, and then drug their co-pilots before flying the plane into a target. One target he identified was the massive petrochemical facility at Abqaiq in Saudi Arabia.

Al Mauretani suggested that Osama bin Laden signal the go-ahead for attacks in Europe with a public message that al-Qaida's patience with Europe had run out. And he had a clear sense of how to finance attacks, saying that al-Qaida in the Islamic Maghreb (AQIM) had "millions" and its leaders trusted him, according to Die Zeit. Mauretani himself was originally from Mauritania in north-west Africa.

Sources briefed on the contents of the letter told CNN that al-Mauretani wrote that al-Qaida Central in Pakistan could only cover the starting costs of the operation against Europe and additional costs would have to be covered by AQIM and others. Analysts tell CNN al-Mauretani's call for the various nodes of al-Qaida to work together was emblemmatic of a shift within the terrorist network towards greater coordination and pooling of resources.

Al-Mauretani added that AQIM had a "great deal of trust" in him, according to the sources. According to analysts the North African operative paved the way for direct cooperation between AQIM and al-Qaida's senior leadership in the late 2000s after he traveled to Pakistan. In late 2011 Moktar Belmoktar, then a senior figure in AQIM, told a Mauritanian journalist that al-Mauretani was the "first direct contact between us and our brothers in al-Qaida."

Bin Laden appears to have liked the ideas in al-Mauretani's letter, and assigned them high priority. Other documents found at his Pakistani compound in Abbottabad suggest he forwarded it to at least one other senior figure in al-Qaida.

In around June 2010, bin Laden wrote to senior Libyan operative Atiyah abd al Rahman, then al-Qaida's head of operations in Waziristan, instructing him to tell the leaders of the al-Qaida affiliates AQIM in North Africa and AQAP in Yemen to "put forward their best in cooperating" with al-Mauretani "in whatever he asks of them."

"Hint to the brothers in the Islamic Maghreb that they provide him with the financial support that he might need in the next six months, to the tune of approximately 200,000 euros," bin Laden wrote.

CNN has learned the document was sent to German prosecutors by the Justice Department after they had asked for any information the United States might have about three men from the Dusseldorf area charged with planning an attack in Germany on behalf of al-Qaida in April 2011. CNN asked the Justice Department about the document but has so far received no comment.

According to Die Zeit, the reason the letter was relayed to the Germans was because al-Mauretani mentions a Moroccan in the document with exactly the same date of birth as Abdeladim el-K, who prosecutors claim was the ringleader of the alleged Dusseldorf cell and trained with al-Qaida in Pakistan in 2010.

Sources briefed on the contents of the document told CNN that al-Mauretani appears to suggest the Moroccan should travel to join up with militants in Somalia if his mission failed.