London — Heavy factional fighting in South Yemen, the poorest and only communist-ruled Arab state, presents both the United States and the Soviet Union with tough problems. South Yemen has been in turmoil since a coup attempt launched Jan. 13 by a hard-line Marxist faction. News reports Wednesday indicated that the armed revolt trying to depose President Ali Nasser Muhammad had been largely put down by forces loyal to the government. The Kuwait News Agency said yesterday that representatives of the groups met in the Soviet Embassy in the capital of Aden. Though some of the revolt's leaders, including ruling Yemen Socialist Party boss Abdel Fatah Ismail were harder-line Marxists than President Muhammad, the Soviet Union apparently backs President Muhammad. The official Soviet news agency TASS called Mr. Ismail's attempt ``counter-revolutionary.''
This apparent Soviet backing for the established government -- together with recent agreements to establish diplomatic ties with pro-western Oman and the United Arab Emirates and overtures to Saudi Arabia -- signals a Soviet shift in favor of stability, at the expense of hard-line Marxist revolutionaries.
The key to the Soviet attitude is seen to be Moscow's anxiety about continued use of Soviet naval and air facilities, which have been improved with Soviet financial help. Both have been closed down in the recent fighting.
British Foreign Office experts, closely following the fate of Aden, a former British colony, say it is not clear whether Soviet, Cuban, or other East-bloc forces stationed in South Yemen have become directly involved in fighting. But they are certain the Soviets would defend their own people and installations if attacked.
Muhammad negotiated a secret base agreement with the Soviets in 1980. But since then, he had been cautiously moving closer to his more moderate neighbors, North Yemen and Saudi Arabia.
US Admiral William Crowe, now chairman of the US Joint Chiefs of Staff, pinpointed the present US dilemma in the Arabian peninsula.
``By 1990,'' he wrote in 1978, ``the United States must pursue foreign and defense policies that preclude Soviet domination of vital oil-producing areas. A prime policy consideration will be the relative ease with which the Soviet Union can move ground and tactical air forces into the Middle East.''
Two things happened soon afterward, justifying Adm. Crowe's concern.
First, the Soviets invaded Afghanistan. Overnight, Soviet air power from Aden in the west and Afghanistan in the east the West's oil supplies and shipping lanes. This happened at a time when Saudi Arabia, the two Yemens, Kuwait, and several Arab Gulf Emirates faced internal strife or tension. Second, the Soviet Union in 1979 proved in a huge exercise that it could airlift within only 36 hours two full fighting divisions from Soviet and Bulgarian bases to South Yemen and its Marxist-ruled neighbor, Ethiopia.
According to Rear Adm. Sumner Shapiro, former director of US Naval Intelligence, the Soviets used Aden's facilities to resupply Ethiopia in its war with Somalia. After the Ethiopia-Somalia war, Adm. Shapiro told a US congressional committee, ``in the Indian Ocean, the main port for [Soviet] logistics and liaison has been Aden.''
Additional military facilities on South Yemen's Red Sea islands face north toward Israel, Egypt, Sudan, Jordan, and Saudi Arabia. Its bases on Socotra Island in the Arabian Sea face US military facilities in Oman.
Aden opened diplomatic relations with Oman and Saudi Arabia after 1980. The US has no ties of any kind with Aden. South Yemen's main income is from the British-built oil refinery and port bunkering and repair facilities. Its meager industry and agriculture are nationalized or collectivized and its 2 million people eke out sparse livelihoods in fishing, farming, dock work, and oil processing.
``The West never seemed to care about the Southern Yemenis,'' said one British expert here. ``South Yemen went Marxist by default. This hasn't happened in any other Arab country. It happened in Aden because we didn't really care, or pay attention. The East-bloc people just naturally moved into the vacuum.''
Ideologically, and sometimes practically, South Yemen supports a broad spectrum of liberation, guerrilla, and terrorist movements. Other than the Soviets, its main allies are Libya and Ethiopia. The three states in 1981 signed a formal alliance, approved by Moscow.
Mr. Cooley, an ABC correspondent based in London, is the Monitor's former Mideast correspondent.