Rhodesia's new multiracial transitional government was tottering under its first major crisis yesterday as one of its four leaders threatened to abandon the two-month old government following the abrupt dismissal of a controversial blackujustice minister.

"Tomorrow will be a day of decision," Bishop Abel Muzorewa said in Salisbury. He said his United African National Council Party would hold an emergency meeting today to discuss its future participation in the Salisbury agreement signed March 3 by Murozewa, two other moderate black leaders and former Rhodesian Prime Minister Ian Smith, a white.

The question of withdrawal was "racing through the minds of a great manys UNAC members, including myself," Muzorewa said. "If my party withdraws, it will be very chaotic so we will weight every move we take."

About 200 UANC supporters picketed outside the party headquarters yesterday in Salisbury waving placards that urged their leaders to "go it alone."

Murozewa said the dismissal of the outspoken Byron Hove from the Justice Ministry could have "disastrous" consequences for the agreement. Muzorewa's contention that he had not participated in the firing was challenged by the two other black leaders on the interim ruling Executive Council.

If Muzorewa carried out his threat to crack the political unity of the government, it would not only deal a severe blow to its credibility aboard, but would also handicap it considerably in the coming elections for black majority rule. Murozewa is regarded as holding the majority support among Rhodesia's 6.7 million blacks.

His withdrawal would come on top of the government's already severe economic and military problems caused by the effects of international trade sanctions and a worsening guerrilla war led by two black leaders who oppose the Salisbury agreement.

Only four days ago the EXECUTIVE Council, which includes Muzorewa, Smith, Rev. Ndbaningi Sithole and Chief Jeremiah Chirau, refused a British-American invitation to attend a conference with the two black guerrilla leaders, Joshua Nkomo and Robert Mugabe. The conference would be held to work out a plan for United Naions-supervised elections involving all the contending parties and thusend the war.

Hove, an appointee of Muzorewa's was dismissed after he refused to retract or apologize for statements advocating fundamental changes in the police and judiciary.

Contradictory statements by Muzorewa and Chirau who currenty has the rotating post of Executive Council chairman, have created confusion about exactly who participated in the decision to fire Hove.

Muzorewa said Friday night that the discharge "was as shocking to me as it was to the general public." The bishop claimed he "was not a party to the decision announced by Chief Jeremiah Chirau."

However, Chirau said yesterday that "all decision-making by the Executive Council has been by all four council leaders." The Agreement signed by the four men in March states that "decision of the executive council will be by consensus."

Sithole confirmed Chirau's version, saying "it was a unanimous decision."

On departing Salisbury for London, Hove said that Muzorewa did not participate in the decision. "My sacking is legally null and void. It is a breach of the internal agreement because Bishop Muzorewa was not at the executive council meeting."

He added: "I feel sorry for my bishop because he's an honest man dealing with a bunch of rogues."

During an interview last week, Hove told The Washington Post that he had urged the government to replace some white judges and to enact a sort of affirmative action program in recruiting and promoting blacks in the police department.

His suggestion attracted rebukes of his white co-minister, Hilary Squires and the head of the army, Lt. Gen. Peter Walls, who said that political interference with law enforcement agencies was not in the spirit of the Salisbury accord.