The U.S. Congress soon will begin a joint House-Senate inquiry into why U.S. intelligence agencies failed to discover and prevent the September 11 terrorist attacks in New York and Washington.

The chairmen of the Senate and House Intelligence committees Thursday announced plans to open the joint investigation later this year.

Republican Porter Goss of Florida, the chairman of the House panel, said, "We are at a threshold time in this country, and there is no doubt that we are going to adjust our intelligence capabilities to fit better the threats that we know that are out there today. One of the clearest of those threats is the terrorist issue."

In testimony to the Senate Intelligence Committee earlier this month, CIA Director George Tenet said intelligence alone cannot stop all terrorist incidents. Mr. Tenet defended his agency saying it uncovered a number of terrorist plots since September 11.

The Congressional hearings are expected to begin in April and will be held in both open and closed sessions. The inquiry will examine whether intelligence agencies are organized, funded and led in a way that leaves the United States vulnerable to further terrorist attacks.