Britain's colonial governor, Lord Soames, and Rhodesian guerrilla leader Robert Mugabe cleared the air over many of their differences today, amid some optimistic signs that the country's black-majority elections starting Wednesday may produce peace.

The two leaders have been at loggerheads almost from the time Soames arrived in Rhodesia in mid-December to steer the country to independence. A British spokesman called their one-hour meeting this afternoon "helpful and important" and Mugabe told a press conference that "bygones are now bygones."

The election, designed to bring about full majority rule after 90 years of white control, threee decades of negotiations and seven years of guerrilla war, could remove this southern African nation from the list of the world's trouble spots, if all sides accept the result peacefully.

Failure of any of the key political parties or their supporters to agree on the outcome, however, could lead to a white-backed coup or a black civil war, causing far-reaching problems for Africa and possibly leading to East-West involvement.

Aside from the upbeat appraisal by both sides of the Mugabe-Soames meeting there were other encouraging developments:

Soames declined to exercise powers to ban Mugabe's party or disenfranchise many of his supporters because of alleged electoral intimidation. Mugabe described Soames' apparent decision not to carry out the threat as a "healthy development."

Gen. Peter Walls, commander of the Rhodesian security forces, held talks yesterday in Mozambique with senior Mozambican military officials reportedly seeking to coordinate actions to prevent a resumption of the war. Walls' forces have repeatedly attacked Mozambique, where most of Mugabe's forces were based, during the last three years, killing thousands and badly hampering the country's economy.

Walls denied that his forces would carry out a coup if Mugabe, an avowed Marxist wins the election. He said in an interview that the country's racial problem has to be settled by a political solution," not militarily. He added that many white officers would probably ojbect to serving a Marxist government, but would resin in orderly fashion rather than revolt.

Mugabe said his forces would join those of guerrila coleader Joshua Nkomo and the Rhodesian security forces to participate in joint military training under the supervision of the Commonwealth monitoring force.

Observers cautioned, however, that the situation in the war-torn country was still dangerous with more than 100,000 Rhodesian troops and reservists deployed and 22,000 guerrillas gathered in assembly points as the country nears the election.

Armored vehicles were deployed at key installations in Salisbury and in various parts of the country in what a Rhodesian military spokesman called a "precutionary" measure.

Mugabe spoke to the press as if he were already prime minister. He talked of the need for reconciliation and added, referring to racial discrimination and seven years of warfare: "We may not forget things of the past, but forgive we must."

He also said he would accept the result of the election no matter who won as long as it was not rigged. He made it clear, however, that he did not think there was any legitimate way he could lose.

At an earlier press conference, Bishop Abel Muzorewa, Mugabe's chief rival and the former prime minister, refused to say whether he would accept the election result.

In a nationwide speech, Soames urged the country's 2.9 million black voters to go to the polls during the three-day election. Results are scheduled to be announced Tuesday.

The election is the culmination of an 11-week return to British-colonial status for the country, which illegally declared independence in 1965 to preserve white-minority rule.

Although nine parties are contesting the 80 black seats in the lower house of Parliament, only three have any realistic chance of forming the country's first accepted black-majority government under the African name Zimbabwe.

The United African National Council, led by Muzorewa, who headed the six-month multiracial government of Zimbabwe-Rhodesia, which was dissolved in December under terms of a peace settlement reached in London. Muzorewa has white backing and favors the continuation of a free enterprise system.

The Zimbawe African National Union, led by Mugabe, whose Mozambique-based guerrila forces did the bulk of the fighting in the seven-year war that killed more than 30,000 people.

The Partiotic Front, led by Nkomo, the 30-year veteran of the Zimbabwe independence struggle who follows a vague socialist line. His forces used neighboring Zambia as a rear base and are militarily aligned with Mugabe although there is some question whether they will form a postelection alliance.

Mugabe is generally expected to win the most seats but not a majority in the 100-member House of Assembly, thus opening the way for bargaining over a coalition. Two other political party leaders, the Rev. Ndabaningi Sithole and James Chikerema, could also play a role in the political negotiations.

For the first time since Rhodesia became a British colony in 1890, the 200,000 white minority population will not have a vote in the direct selection of the leadership of the nation's 7 million people.The 20 white seats have already been won by white former prime minister Ian Smith's Rhodesian Front party, which still could play a key role in forming a coalition.

Lord Soames hopes to be able to name a prime minister and carry out his final act -- installation of an independent government -- by mid-March, thus ending a three-month recolonization of Rhodesia.