Toronto — An American newspaper reported Wednesday that al-Qaeda “sleeper cells” in Canada and the United States have communicated with each other as recently as this month, probably to plan attacks in the United States.

A report on the Washington Post's Web site said the disclosure came from Canadian intelligence experts after last week's arrest of Mohamed Harkat, 34, a pizza delivery man in Ottawa who is suspected of being associated with Osama bin Laden's al-Qaeda network.

The Post reported that Canadian authorities decided to arrest Harkat shortly after he allegedly made calls to suspected al-Qaeda members in the United States, quoting Reid Morden, former director of the Canadian Security Intelligence Service, who has been in contact with the Canadian spy agency on the matter. The newspaper said Morden confirmed comments made earlier by Canadian officials speaking on condition of anonymity.

However, it was not clear precisely what triggered the arrest of Harkat. The nature of the phone calls to the United States with other al-Qaeda members is also not known.

CSIS has suggested that Mr. Harkat was a “sleeper” terrorist, waiting for orders to execute an attack in Canada or elsewhere. However, Harkat's lawyer, Bruce Engel, said last week that his client was “not knowingly associating with anybody involved in terrorism.”