The head of the U.S. Federal Bureau of Investigation says he is concerned that terrorists may target upcoming events in the United States and other countries because of the impact the Madrid train bombings had on Spanish elections.

FBI Director Robert Mueller has told the Associated Press there is, "a window of time" until the U.S. presidential election in November when terrorists may want to influence events in the United States or overseas.

U.S. officials are concerned terrorists may target the upcoming U.S. political conventions, and the summer Olympic games in Athens, Greece in August.

The news agency quotes the FBI chief as saying terrorists may be changing their focus from more secure targets, such as airports and government buildings, to less secure "soft" targets. He also warned that Islamic militants have begun recruiting local sympathizers in potential target areas in order to arouse less suspicion.

Mr. Mueller pointed to last year's May 16 suicide bombings in Casablanca, Morocco, saying local Islamic militants with possible ties to the al-Qaida terror network are suspected in that attack.

Mr. Mueller also praised the counterterrorism efforts by Pakistan as well as Saudi Arabia, which he called "a very inhospitable place for al-Qaida."