Chances for reaching an internal peace settlement in Rhodesia any time soon diminished yesterday when Bishop Abel Muzorewa, leader of the United Africa National Council, emerged from a meeting with his advisory group and said he was increasing his political demands.

Muzorewa, the leading black negotiator in the talks with the white minority government, announced that there would be no preliminary agreement on a constitutional settlement providing for black majority rule without an accord on bringing black nationalist guerrilas into the country's armed forces.

The announcement followed a four-hour meeting Muzorewa had with his 360-member national consultative assembly. It was the first time Muzorewa had publicly insisted that incorporation of the black guerrillas into the armed forces be given priority.

This, Muzorewa said, was the 'most vital and crucial issue" facing the deadlocked, two-month-old peace talks involving himself, Prime Minister Ian Smith, the Rev. Ndabaningi Sithole of the African National Council and Chief Jeremiah Chirau of the Zimbabwe United People's Organization. Zimbabwe is the black African name for Rhodesia.

The other black negotiators have indicated they were willing to wait and have the transitional government work out details on the armed forces issue.

Political analysts believe there has been pressure from the grassroots - such as from the consultative assembly - that has forced Muzorewa to dig in his heels on some issues that until now he was willing to give way on.

Muzorewa now apparently feels that solidifying his credibility with his own constituency - even at the cost of slowing down or even torpedoing the constitutional talks - is more important than rushing to a conclusion out of fear that the externally based guerillas will make further inroads in the country.

Muzorewa made it clear at a news conference yesterday that, backed by a "fresh mandate" and the delegates "full and unreserved confidence," he was going to stick by his position on the question of how many seats should be alloted to the whites in the new parliament.

For more than two weeks Muzorewa has refused to endorse a plan that the other negotiators claim he once approved.It provides that 28 seats out of the planned 100 in the proposed parliament would be set aside for whites who are outnumbered 30 to 1 by the country's 6.7 million blacks.

Muzorewa has countered with a proposal that 20 legislators be elected by whites and the eight others by white and black voters. This would seem to be a plan to have blacks help elect liberal whites not controlled by Smith's conservative Rhodesia Front Party.

Smith is still credited with trying to persuade Joshua Nkomo, coleader of the patriotic Front which controls the guerillas outside Rhodesia, to returen home and contest elections that would usher in black rule.

Since Nkomo could count on probably no more than 20 percent of the electorate - in light of the country's tribal political traditions - he would need white votes to achieve his dream of becoming the first black prime minister.

Muzorewa touched on such a possibility in speaking of "growing fears among our our people that Smith is going to gang up with Sithole, Chirau and anybody else."

Asked if he was not worried about incorporting thousands of guerrillas into a new national army after back majority rule, the bishop replied: "You'll need a big army for a long time because there'll be mischievous persons" who will not accept an internal solution.

The conventional wisdom is that the Patriotic Front leaders will boycott such a solution and continue to try to take over country by military means.