Astronomer Carl Sagan and other scientists asked the secretary general of the United Nations to urge a cease-fire in the Persian Gulf war so environmental damage can be assessed.

"As realization of our greatest fears materialize, we plea for a pause in hostilities to take place immediately, allowing for a full assessment of what could begin with regional disaster . . . within the tight ecosystem of the gulf region and end with a catastrophe of incalculable proportions," they said in a letter to Javier Perez de Cuellar.The letter, dated Wednesday, was signed by 11 scientists, including Sagan, a professor at Cornell University who hosted the public television series "Cosmos."

The letter asked the U.N. General Assembly and Security Council to pursue a cease-fire.