The Prime Minister of tiny Belize, a British colony in Central America, is resisting pressure from London and Washington to give a slice of his land to the military government in neighboring Guatemala.

A consortium of oil companies headed by Exxon is now drilling for oil on the territory Belize has been asked to yield as the price for its independence.

But after two days of talks here with British Foreign Minister David Owen. Belizean Prime Minister George Price declared last night that "no settlement was reached . . . We still maintain no land cession."

In the House of Commons, Owen promised that Britain will "defend and uphold" any decision taken by the 140,000 people of Belize against giving up their land. Belize was formerly known as British Honduras.

In the background is Teerence Todman, the U.S. assistant secretary of state for Latin America. He has been in Guatemala City while Price and Owen talked here. Todman saw Price before he came to London and the Belizean said that Todman told him there could be no solution without the surrender of land.

The affairs of a country of 9,000 square miles and 140,000 population, wedged between Mexico's Yucatan peninsula and Guatemala, would not normally involve high-powered officials like Owen and Todman. But the fact that the land Belize is asked to yield probably contains oil, either on shore or off, has involved top-level diplomats in the little colony's affairs.

The British are eager to get out. The colony ties up six Harrier jets, a garrison of troops and a Royal Navy contingent and continually threatens to involve London in a clash with Guatemala. Britain and Guatemala held talks last July in Washington after rumblings of a Guatemalan invasion of Belize.

Britain is suggesting that it could offer an independent Belize a guarantee against invasion provided Guatemala was satisfied by receiving the piece of land it wants.

Price told reporters: "We can't afford to oppose the people who defend us." For the time being, however, he is doing just that.

He maintained that Guatemala's legal claim to the land, based on Britain's failure to build a road from Guatemala City to the coast under an 1859 treaty, has no standing. Price insisted that Belize, unlike Guatemala, has functioning democratic institutions and respects human rights. Any cession, he said, could only lead to further demands from Guatemala. Finally, Price said the prospects of oil wealth were another good reason to hang on.

The United States has been sympathetically involved in Guatemalan affairs at least since the CIA helped overthrow the leftist government of Jacobo Arbenz in 1954.

Price said a plebiscite will be held, presumably on the question of independence-plus-cession or continued colonial status.