The Soviet Union rejected yesterday as "crude blackmail" the notion that Soviet military involvement in the Horn of Africa could have an adverse effect on the U.S. Soviet Strategic Arms Limitation Talks.

Calling such a warning "dangerous" and "unacceptable," the authoritative daily Pravda rejected a weekend State Department statement which for the first time indirectly linked the[WORD ILLEGIBLE] of SALT talks and the Ethiopian Somali conflict.

The Soviet statement was not a response to a more direct linkage made Wednesday by presidential national security adviser Zbigniew Brzezinski, although it foreshadows Moscow's reaction.

However, U.S. officials viewed Pravda's comments on the SALT negotiations as containing a Kremlin message on this crucial aspect of U.S. Soviet relations. They pointed to President Carter's statement on the subject yesterday which shifted the establishment of any such linkage to Congress, which would have to approve an eventual arms pact.

Moscow's lack of concern for repeated U.S. complaints about Soviet involvement in Ethiopia and Soviet intransigence at the Belgrade conference reviewing European security and human rights have brought about a noticeably cooler climate in U.S.-Soviet relations.

A senior State Department official told newsmen yesterday that the 35-nation Belgrade meeting would end "within days" without producing a substantive document.

Apart from agreeing to hold another review in 1980, the Belgrade conference was expected to end with a brief communique which is, in effect, an agreement to disagree.

While acknowledging that the set-back at Belgrade has "contributed to cooling" U.S.-Soviet relations, the senior official said it has not brought about any real deterioration between the two countries. He also denied any linkage between the SALT negotiations and the Horn of Africa.

Pravda in a commentary yesterday attacked the linkage as "unsavory and dangerous playing with the main problems of international security and detente."

It said: "Attempts are being made with the assistance of official circles in Washington to link directly the problem of the Horn of Africa -- interpreted in an anti-Soviet way -- with the outcome of the Strategic Arms Limitation talks.

"It is not difficult to see that this smacks of crude blackmail which is impermissible in international relations."

The commentary warned that by trying to tie in two problems "with nothing in common," the Carter administration could aggravate overall U.S.-Soviet relations.

While disavowing any linkage to SALT negotiations, U.S. officials continued to emphasize the risks posed by the continued Soviet and Cuban military buildup in the Horn of Africa.

A State Department spokesman said yesterday that the Cuban presence in Ethiopia was increasing by roughly 200 men a day. Last week, Brzezinski disclosed that Cuba's military force in Ethiopia was estimated at up to 11,000 men and yesterday secretary of State Cyrus Vance said that two Soviet generals was directing some of Ethiopia's military forces.

The number of Soviet military advisers in Ethiopia is estimated at 1,00. The Soviet Union reportedly supplied the Ethiopians with 400 tanks and 50 Mig jet fighters.

Moscow has insisted that it is perfectly within its rights to provide military assistance at the request of the Ethiopian government. Ethiopia is tryin to dislodge Somali forces from the Ogaden region, as area of Ethiopia populated by ethnic Somalis and taken over by Somalia last summer.