Former Cambodian head of state Nordodom Sihanouk met with top U.N. officials today in an attempt to gain a Security Council hearing on the Hanoi led invasion and takeover of his country.

But the Soviet Union blocked the attempt today on grounds that Sihanouk represented a government that no longer existed.

Soviet Ambassador Oleg Troyanovsky also informed U.N. Secretary General Kurt Waldheim that the new government in Phnom Penh would soon send its representatives to the United Nations and that they would participate in any Security Council discussion of the Cambodian situation.

A U.N. spokesman said, however, that Security Council members agreed to hold a public meeting on Cambodia Thursday afternoon and that during the meeting the 15-nation council would decide whether to hear Sihanouk.

The agreement, reached in private consultations, was that Thursday's agenda should include a telegram sent by the Pot Pol government requesting an urgent meeting of the council to consider the Cambodian fighting.

China, the main ally of the deposed government of Premier Pol Pot, and the United States both lobbied for the convening of a meeting on Cambodia.

"We take the position that this is a government recognized by the United Nations which has asked for hearing because they were invaded," U.S. Ambassador Andrew Young said. "It would be most cynical for us to allow governments to be stricken from the roles simply because another power moves in and says it no longer exists.

"I would be reluctant if I were the Soviet Union and Vietnam to admit that the government no longer exists because it seems as though they knew too much about it to be innocent of it," Young said.

Young reiterated the U.S. condemnation of the Pol Pot government's human rights record, but said that "we defend the territorial integrity of a nation no matter what we might think of that nation."

Sihanouk met with Waldheim and Jamaica's Donald Mills, the current Security Council president, to argue that he is the representative of the only legal government in Cambodia. The Pol Pot government was ousted by the Vietnamese and Cambodian insurgents on Sunday.

"I do not want a moral condemnation of Vietnam," Sihanouk told reporters. "I just want the Vietnamese to withdraw unconditionally and very quickly go home."

The former Cambodian leader, who was kept under virtual house arrest for three years by the government he now says he represents, said he expected to meet with Secretary of State Cyrus Vance.

Vance said through a Washington spokesman that he would meet Sihanouk if a formal request is made.

The Cambodian complaint is the first direct confrontation between Moscow and Peking over a subject of vital interest to both. Each has veto power, as do the United States, Britain and France.

The Soviet Union supports Vietnam and quickly recognized the new government in Phnom Penh.