BEIRUT, FEB. 22 -- American Lt. Col. William Higgins appeared on a brief videotape issued today by his Iranian-backed captors. He listed their demands for his release in this first such appearance since he was kidnaped last Wednesday.

Higgins was unshaven and expressionless as he read from a prepared text in the 70-second videotape. It was accompanied by a statement signed by the Organization for the Oppressed on Earth, a shadowy group believed to be a front or label for underground Iranian intelligence work in Lebanon.

The demands read by Higgins reiterated those spelled out Friday in a statement signed by the same group, in which it branded him as a spy gathering information for the Central Intelligence Agency under United Nations cover.

Higgins, the chief of the Lebanon unit of observers attached to the U.N. Truce Supervision Organization, said his captors demand the withdrawal of Israeli forces from all occupied territories in Lebanon, the release of Lebanese and Palestinians detained in Israeli jails and an end to U.S. involvement in Lebanon and the Middle East.

"In order to get me released these demands have to be met," he said. Higgins, 43, who was kidnaped by three bearded gunmen while traveling near the city of Tyre, wore a grayish-green sweatshirt.

The message emphasized the group's demand that the United States freeze its diplomatic role in the Middle East. Washington must "stop sending delegations to the Middle East area in order to circumvent the gains of the Islamic revolution in occupied Palestine," it said. Secretary of State George P. Shultz is to visit the region this week.

Iran has insisted that the Palestinian uprising in the West Bank and the Gaza Strip is due partially to a rise in fundamentalist fervor in the region and appeared to signal in the message its fear that any U.S. role may exclude Iranian influence.

{"All statements made by hostages are made under duress," said State Department spokeswoman Phyllis Oakley, echoing a similar comment by White House spokesman Marlin Fitzwater.}

In southern Lebanon, militiamen of the mainstream Shiite Amal movement and soldiers of the U.N. Interim Force in Lebanon persisted in a search for Higgins. They moved deep into the countryside, from village to village, combing fields and the densely wooded banks of the Litani River.

The Organization for the Oppressed on Earth advised Justice Minister Nabih Berri, who heads the Amal movement, to stop Amal military operations against more radical Shiites, including those of the Iranian-backed Hezbollah (Party of God). Amal has arrested scores of Hezbollah supporters in the Tyre region in its search for Higgins.

There has been a vitriolic argument between Amal and Hezbollah, which has declared support for Higgins' abduction. A statement by 45 Shiite religious scholars who met in Tyre this afternoon underlined fears of conflict between the two groups.

"The situation has reached the dimensions of utmost danger, to which we must not react but which we cannot forgive," the statement said. The mullahs appeared to criticize Amal's search, demanding the release of detainees, and pledged allegiance to Iranian leader Ayatollah Ruhollah Khomeini.

Amal has shown unprecedented resolve in its effort to rescue Higgins, whose abduction it considers a challenge to its authority in southern Lebanon. Higgins was kidnaped minutes after leaving a meeting with Amal's senior political officer in Tyre, Abdel Majid Saleh.

A senior Amal officer in Beirut in contact with field commanders in southern Lebanon said Amal had intensified its dragnet around Tyre and Nabatiyeh, multiplying the number of moving checkpoints and searching cars driving in and out of the area. "Our hunt for Higgins will not die down. Our determination is as strong as it was on the first day. We cannot stop now," said the Amal official, who declined to be named.

The intra-Shiite conflict between the Iranian-backed extremists and the more moderate Amal has been brewing since the wave of kidnapings of foreigners in Lebanon began. Fundamentalists accuse Amal of being overly protective of "suspect agents of espionage," and Amal has accused the kidnapers of being primarily motivated by ransom money.

"Kidnaping operations which have targeted foreigners in Beirut under the slogan of combating espionage soon wind down to money deals, and vast amounts of cash that are distributed among various factions," Amal said yesterday in a statement.