An arrest warrant has been issued by Yugoslav authorities for dissident writer Mihajlo Mihajlov, now believed to be in the United States, on charges of writing propaganda against the state, legal sources said today.

Mihajlov, 46, who has been imprisoned three times during the last 15 years, left Yugoslavia in May 1978 to visit his mother and sister in the United States and give lectures. He has postponed his return to Yugoslavia on several occasions, but friends said he is now planning to return in September.

For the last several months, Mihajlov has been living with relatives in Alexandria, Va.

Outside of former Yugoslav vice president Milovan Djilas, who fell into disgrace for advocating a more liberal system of government, Mihajlov is probably Yugoslavia's best known dissident. He is the author of a book called "Moscow Summer," which angered the Soviet Union. Mihajlov last was released from prison in November 1977 under an amnesty after serving half of a seven-year sentence.

In an interview at the time of his release, Mihajlov said he intended to continue to speak out against alleged human rights violations in Yugoslavia - even if it meant another jail sentence.

Yugoslav legal sources said that if he is convicted of the new charges against him - which include association with hostile emigre organizations - Mihajlov could be sentenced to between five and 10 years' imprisonment.

Last December, the Belgrade daily Politika accused him of having extensive contacts with Croat and Serb terrorist organizations abroad.

Foreign observers said that the aim of issuing the arrest warrant against Mahajlov at this time could be to discourage him from returning to Yugoslavia, thus avoiding an embarrassing dilemma about how to deal with him.