A Church of England envoy said today that he was "in touch" with the captors of four Americans held hostage in Lebanon and his effort to arrange their release was progressing.

Terry Waite, a lay representative of Archbishop of Canterbury Robert Runcie, arrived in the Lebanese capital yesterday. He told reporters asking today about his contacts with the Moslem Shiites believed to be holding the Americans: "We are in touch in several ways. Progress is being made and we are moving forward."

Waite, who has negotiated the release of Britons held in Iran and Libya, warned the reporters that if they followed him as he moved around Beirut it could block his efforts and endanger the lives of himself and the hostages.

"I would like to make a plea that I'm not to be followed by anybody because if that happens then it might jeopardize my own safety and the safety of other people. It is extremely important because of the great, great sensitivity of the situation that I am left totally alone because anything I have to do beyond this point would have to be entirely by myself."

"We have reached a very critical and a very dangerous point," he said. "We have procedures being worked out now."

Waite, a tall, bearded man who is the archbishop's adviser on international affairs, traveled to Iran in 1981 to arrange the release of three missionaries, and met with Libyan leader Muammar Qaddafi last year to obtain the freedom of four British citizens there.

Diplomats here observed that Waite would not have come to Beirut had there not been a fair chance for accomplishing something.

Waite told the journalists that the kidnapers were taking a chance in meeting him and warned, "Any wrong move and people could lose their lives."

Waite's mission has aroused the interest of the foreign press corps here. American television correspondents flew into the Lebanese capital yesterday with camera crews to trail the church emissary.

Waite called on journalists to let him get on with his task without undue publicity after he saw cameramen and photographers outside an apartment where he is staying in Moslem-controlled west Beirut.

Waite moved out of a west Beirut hotel late last night and drove to an undisclosed location escorted by Shiite Moslem militiamen of the Amal movement. Islamic Jihad, an underground organization that has claimed responsibility for the kidnaping of eight Americans since March 1984, allowed four hostages to write open letters last week to Reagan, their families and the archbishop of Canterbury.

In the letters, they appealed for quick action to arrange their release.

In a communique delivered to a Beirut newspaper Oct. 4, Islamic Jihad announced the execution of U.S. Embassy political officer William Buckley.

It distributed a blurred photograph of the missing diplomat wrapped in a white shroud to foreign news agencies eight days later, but the U.S. government has not confirmed his death.

Last May 15, the same group proposed to release four Americans, including Buckley, if 17 prisoners convicted of bombing U.S. and French targets in Kuwait in December 1983 were freed. Two other Americans were kidnaped later in May and in June.

The letters issued by the hostages last week were signed by Terry Anderson, bureau chief of The Associated Press; the Rev. Lawrence Jenco, head of Catholic Relief Services in Beirut; David Jacobsen, director of the American University hospital, and Thomas Sutherland, dean of the school of agriculture at the American University of Beirut.

Presbyterian minister Benjamin Weir was freed Sept. 14 and delivered an appeal to President Reagan to move quickly to gain the hostages' release.

American University librarian Peter Kilburn has been missing since Dec. 3.

His photograph has never been distributed, as have pictures of the others, and Weir, who met with the four others, said he knows nothing about the librarian.

Although there are no guarantees that Waite will succeed in securing the release of the Americans, recent signs by their captors suggest they may be ready to negotiate a face-saving way out of the impasse.

The Reagan administration has said it will not bend to wishes of terrorists but has left the door open for negotiations and talks that could lead to the freedom of the captives.

After his release Weir said the kidnapers were getting impatient with the lack of progress in obtaining the release of the 17 prisoners from Kuwaiti jails.

The letters by the four hostages last week also stressed that their captors would not tolerate a prolonged deadlock.

A senior U.N. envoy who arrived here from Israel today indicated that U.N. Secretary General Javier Perez de Cuellar was "very concerned about the fate of the hostages."

Jean-Claude Aime said his main mission here is to explore ways of enabling a U.N. peace-keeping force in south Lebanon to fulfill its mandate by deploying all the way down to the Israeli border.

Aime said he had also discussed with President Amin Gemayel the fate of a British U.N. employe, Alec Collett, who was kidnaped by a separate Moslem group March 25. Collett, a journalist, was on special assignment for the U.N. Relief and Works Agency. He and four Frenchmen are also missing.