Libyan leader Col. Muammar Qaddafi, one of the Third World's harshest critics of the United States, praised President Carter today as a "good, religious man" and suggested that the two men work to improve relations between their countries.

As a start, Qaddafi suggested in a speech, two countries should raise the level of their diplomatic representation and the United Sates should allow the delivery of eight C-130 cargo planes that Libya purchased four years ago but never received.

Qaddafi has made similar proposals in the past but today's, reported by the official Libyan Arab Revolution News Agency, was believed to be the first addressed specifically to Carter.

The United States has rejected previous efforts by Tripoli to improve relations, saying that this is impossible while the Libyan government continues to support terrorism in Africa, the Middle East and other areas of the world.

Qaddafi's remarks were made at Darnah in eastern Libya during a rally marking the seventh anniversary of his government's closing of Wheelus U.S. Air Force Base in Libya.

"President Carter seems to be a good man, a religious man," Qaddafi said. "He can reduce the tensions between his people and the people of the world."

The United States, Qaddafi said, has "no justification at all" in not accepting a Libyan ambassador.

"This is one condition for the American president to prove that his is actually moving toward changing American policy and easing the intensity of hostilities between his people and other peoples," Qaddafi was quoted as saying.

A charge d'affaires has headed the 13-person U.S. diplomatic mission in Tripoli for five years, since the departure of the last U.S. ambassador following the closing of the big Wheelus air base. The Libyan mission in Washington also is headed by a charge d'affaires.

Qaddafi also called on Carter to lift the U.S. export ban on the C-130 transport planes "because they are the property of the Libyan Arab people," news agency reported.

The C-130's were sold to the Libya in 1973 in an agreement negotiated before the October 1973 Mideast war, but the State Department blocked delivery of the aircraft and spare parts because of the generally bad relations with Libya.

The State Department also rejected an application by Lockheed Aircraft Corp. to bring 56 Libyan air force personnel to the United States for training in the maintenance of the C-130's.

The news agency said Qaddafi, in his speech today, proposed converting the aircraft into civilian planes "if the Americans are afraid to deliver them in their military form."

Most Libyan military hardware has been bought from the Soviet Union and France, and Libyan units have trained in the Soviet Union, but Libyan officials have told Americans privately they would buy U.S. equipment if they could.

A strict follower of Islam and therefore strongly anti-Communist, Qaddafi has always emphasized that "we deal with the Soviet Union on a commercial and not an ideological basis."