The decision by the International Committee of the Red Cross to end food shipments to Cambodian border zones controlled by Khmer Rouge guerrillas has focused attention on a chronic problem for relief operations in Cambodia -- diversion of aid supplies to soldiers.

The Red Cross made its last delivery of food to the Khmer Rouge settlements just south of the Thai border town of Aranyaprathet on June 17, according to a Red Cross spokesman. There are no plans to resume delivery, he said.

The Red Cross had been supplying food for 55,000 persons, although some relief workers believe the Khmer Rouge inflated the figure to obtain extra supplies for stockpiling. Many residents of the settlements are known to be soldiers loyal to Pol Pot, the Cambodian leader ousted in 1979 after Vietnamese troops invaded that country.

Deliveries were ended, the spokesman said, because the Khmer Rouge authorities were not meeting the Red Corss' three standard conditions for distribution of supplies: separation of soldiers and civilians, guarantees of security, and access to monitor distribution.

Similar problems at camps controlled by anticommunist Khmer Serei guerrillas north of Aranyaprathet might force suspension of food deliveries there, he said. Aid officials estimate that more than 100,000 people live in the three largest camps.

It is unclear whether other aid groups will be allowed to replace the Red Cross if the agency sticks by its decision.

Since the feeding operation began last October, experienced relief officials have said that they have never worked in a place where the task of feeding hungry people has encountered so many political obstacles.

The agencies must deal with authorities from the three contending Cambodian factions, each of which insists that it is the only legitimate conduit to receive and distribute aid. Much of the aid is then subverted to strengthen the armed forces and civil service of each party.

The Red Cross and U.N. International Children's Fund (UNICEF) have delivered an estimated 150,000 tons of food and seed to the Heng Samrin government, installed in Phnom Penh by a Vietnamese invasion force 18 months ago.

Another 90,000 tons have been moved across the Thai border into enclaves controlled by Khmer Rouge and Khmer Serei guerrillas. Many of these provisions eventually enter zones controlled by Heng Samrin through an unofficial "land bridge" of Khmers driving oxcarts and bicybles.

The land bridge ceased operating two weeks ago when Vietnamese forces made an incursion into Thailand and dispersed the main staging site near the village of Nong Chan.

The Red Cross' belated decision to get tough on the border was first revealed in a closed-door session of representatives of donor countries in Bangkok last week.

Many analysts see the decision as a gesture of appeasement to Phnom Penh. In their view, the Red Cross wants to get out of the border feeding operation in hopes of winning close cooperation in Phnom Penh and improved distribution inside Cambodia.

Other theorists say that the Red Cross is bluffing to make the Thais provide better protection against fighting in the camps and to persuade the guerrilla units to leave the area where civilians are living.