The State Department, concerned about an atmosphere of rising tension in the Middle East, declared yesterday that current U.S. military activities there are designed "to defuse the tensions through deterring possible hostilities."

As explained by State Department spokesman Dean Fischer, the U.S. statement was meant to calm increasing jitters reflected in press reports and other data coming from the troubled region.

Among the reports that drew U.S. attention were those of military alerts in Egypt, martial law in Sudan and increasingly strident charges from Libya and the Soviet Union of a planned U.S.-sponsored invasion of Libya. All this evidently contributed to fear that parties on all sides of the Middle East passions may be overreacting to Washington's initiatives.

Officials denied that any specific troop movements by nations in the area lay behind issuance of the statement. Fischer said, however, that there was U.S. concern "that an escalation of tensions and rhetoric could feed on itself and lead to the precise thing we are trying to avoid, an outbreak of hostilities."

Fischer said the U.S. military activities are "confidence-building and deterrent in character" and, together with expedited arms shipments to Sudan and perhaps Egypt, "are a modification and telescoping of long-contemplated actions designed to enhance the security of the area."

On Wednesday, the United States dispatched two Airborne Warning and Control System aircraft to Egypt in what Secretary of State Alexander M. Haig Jr. called a demonstration of U.S. ability to move into the region militarily "under emergency conditions." Haig said the AWACS in Egypt would be "a temporary presence" as part of Operation Bright Star, a mid-November to mid-December military maneuver scheduled to include U.S. and Egyptian ground forces activity and B52 bombing exercises near the Egyptian-Libyan border.

Yesterday's statement said the AWACS would be deployed to Egypt "on an interim basis," a period that Fischer refused to define. Before Haig spoke Wednesday, the spokesman had announced that the planes would be assigned to Egypt for "an indeterminate period." Secretary of Defense Caspar W. Weinberger, traveling to Europe, described the dispatch of AWACS as a first step in a long-term program of improving Sudanese air defenses, which suggested a lengthy deployment.

Libyan and Soviet broadcasts and press statements are increasingly charging that the sending of AWACS and the extensive Bright Star maneuvers are preparations for a Sudanese invasion of Libya.

Sudanese President Jaafar Nimeri has been quoted several times in recent days as threatening to launch an attack into Libya to depose his sworn enemy, Libyan leader Muammar Qaddafi. State Department officials said they do not consider such an attack to be likely or even practical, however.

In remarks to reporters at the daily State Department briefing, which was postponed about two hours while the special statement was being drafted, Fischer pointed to reports of military alerts in Egypt and of the movement of Egyptian troops to Sudan, among others, as the cause for the official concern. At the same time, the spokesman said he could not confirm whether the reports are true.