News of Mr Awlaki's trial came as it emerged that in September US intelligence officials intercepted parcels of books, papers and CDs that had been shipped to Chicago from Yemen and considered the possibility that they might have been test runs for terrorist attacks, officials say.

Now the intelligence officials believe that the shipments, whose hour-by-hour locations could be tracked by the sender on the shippers' websites, may have been used to plan the route and timing for the two printer cartridges packed with explosives that were sent from Yemen and intercepted in Britain and Dubai on Friday.

When US counter-terrorism agencies received information linking the first packages to al-Qaeda in the Arabian Peninsula (AQAP), the terrorist network's branch in Yemen, they stopped the shipments in transit and searched them, officials said.

They found no explosives, and the packages were allowed to be delivered to what appeared to have been ''random addresses'' with no connection to the terrorist group in Chicago.

''At the time, people obviously took notice and - knowing of the terrorist group's interest in aviation - considered the possibility that AQAP might be exploring the logistics of the cargo system,'' an official said.

The apparent test runs may have permitted the plotters to estimate when cargo planes carrying the doctored toner cartridges would be over Chicago or another city. That would conceivably enable them to set timers on the two devices to ignite explosions where they would cause the greatest damage.

One of the officials said that when the US intelligence agents had received a tip from Saudi intelligence officials last week that bombs might be on cargo flights to Chicago from Yemen, analysts had ''recalled the incident and factored it into our government's very prompt response''.

On Monday Germany, France and Britain said they had banned cargo shipments from Yemen, following a similar move by the US. Britain prohibited passengers from carrying printer cartridges aboard flights and Germany halted passenger flights from Yemen as well.

Yemen yesterday announced charges against Mr Awlaki, accusing him and two other men of plotting to kill foreigners and of being members of al-Qaeda. The charges against Mr Awlaki were announced in his absence as part of the trial of Hisham Assem, who is accused of killing a Frenchman in an attack on October 6.

No evidence has been made public linking Mr Awlaki to the printer cartridge bombs, but intelligence officials believe that he played a role in the alleged failed bombing of a Detroit-bound aircraft on Christmas Day last year.

Mr Awlaki, believed to be hiding in Yemen's mountains, has publicly called for more attacks on the US. The Guardian reported that a gifted student convicted yesterday of attempting to stab to death a former British government minister was ins-pired by his internet sermons.

A US official said that the addresses on the packages in the foiled attacks last week were outdated addresses for Jewish institutions in Chicago. The addresses are one reason that investigators now believe the plan may have been to blow up the aircraft, since there were no longer synagogues at the Chicago locations.

US counter-terrorism officials said they were taking a new look at the crash of a United Parcel Service cargo plane in Dubai on September 3 in light of the explosives plot. An initial investigation of that crash and on-board fire, in which two pilots died, found there was no evidence of an explosion.

At the core of the latest parcel plot, US officials believe, was Ibrahim Hassan al-Asiri, the alleged al-Qaeda bomb maker.

Agencies