WASHINGTON (AP) _ A New York congressman on Tuesday proposed that a commemorative postage stamp be issued in memory of the seven Challenger astronauts killed when the shuttle exploded last week.

In a letter to Postmaster General Albert V. Casey, Republican Rep. Raymond McGrath said that while a week had passed since the accident, ''sorrow and disbelief remain in the hearts and minds of all Americans.''

Because Christa McAuliffe was the first teacher-astronaut, he suggested that the design for the stamp could be solicited through a nationwide student competition.

''While we can never do enough to pay tribute to these American heroes, a commemorative stamp is one simple way that we honor their bravery and their sacrifice,'' McGrath said.