NEW YORK - Ken Schaffer has solved the gnawing question of how to conduct reliable daily business communications for Houston oil companies trying to reach their partners in the heart of the Siberian Oil fields.

With the Soviet telecommunications infrastructure in such disrepair, almost every Western company trying to do business in the Soviet 'Union has agonized over how to make a direct phone call, or send a fax or a telex halfway around the world without a hitch.

"Even if a company has the best intentions, if you can't talk to your partner, then the frustration will make you walk away from the deal," said Mr. Schaffer, vice president of Belka International Inc., a New York-based telecommunications company.

Belka's satellite phones fit in a suitcase and connect with the London-based Inmarsat worldwide satellite system to enable direct phone, fax, telex and data transmissions between the United States and any point in the world, including the oil fields of Siberia.

One U.S. oil company says the satellite phone has dramatically changed the way it does business in the Soviet Union. In fact, Anglo-Suisse L.P., based in Houston, has begun drilling at two oil wells in western Siberia, near the city of Raduzhny, with the help of the satellite phone.

"It's tremendously helpful to be able to communicate on a daily basis. It speeds the overall operation and allows us to make decisions quicker and to service our operation efficiently," said Charles Brunet, vice president of Anglo-Suisse, during a telephone interview.

Anglo-Suisse is one of several Western oil companies vying for stakes in the risky, but potentially profitable Soviet oil market. Anglo-Suisse is one of the only U.S. companies actually drilling in the vast Soviet oil fields and exporting that oil on Western markets.

Mr. Brunet said the company is expanding its oil drilling operations near Raduzhny and is currently exporting Soviet oil to world markets via Soviet pipelines to the Black Sea port of Novorossiysk, and then by tankers to Western markets.

Mr. Schaffer said several major U.S. companies including, Anglo-Suisse, Chevron Corp., Mobil Corp., Conoco Inc. and General Motors Corp. already are using the satellite phone system to conduct daily business communications between their home offices in the United States and the sites of their ventures in the Soviet Union.

Belka already has sold 15 units at $75,000 each to Western companies, plus additional line charges. The company provides turnkey services to its customers, including authorizations, licenses, Customs clearance and weaving them through the bureaucracy at local, republic and central ministerial levels.

Several other Western companies are investing in the Soviet telecommunications industry, looking for opportunities to improve gateway switches for long-distance telephone service and for cellular networks.