Vietnam accused the United States today of seeking to help China expand its invasion of Vietnam.

In its strongest denunciation of United States' relations with China since the invasion began, Hanoi said Washington is trying to restrain Vietnam and its friends "and to create conditions for China to escalate its war of aggression on Vietnam."

A Radio Hanoi commentary dismissed U.S. statements that it disapproves of the invasion as a cover up for "the fact that the United States is encouraging and taking advantage of China's war of aggression."

It compared U.S. Ambassador Andrew Young's call at the United Nations for a withdrawal of Chinese forces from Vietnam linked to a with-drawal of Vietnamese forces from Cambodia to Johnson administration efforts to Johnson administration efforts to pressure Hanoi into abandoning its war against South Vietnam.

President Johnson demanded that North Vietnam stop fighting in South Vietnam "in exchange for U.S. deescalation of the air war of aggression against North Vietnam," the radio said. It called this a comparable confusion of "the aggressors with the victims of aggression."

It also denounced Washington for sending Treasury Secretary W. Michael Blumenthal to Peking "to hoist the flag at the U.S. Embassy in Peking" while Chinese troops are in Vietnam.

The Chinese invasion on Feb. 17, the commentary said, followed Chinese Vice Premier Teng Hsiao-ping's visit to the United States and normalization of relations between the two countries.

Accompanying its diplomatic moves, Hanoi said, were American statements that it had moved part of its fleet to waters off the coast of Vietnam and China.

Hanoi said the Chinese invasion was in danger of becoming enlarged, but there was no evidence that Chinese troops have moved from the hilly terrain around Langson, 85 miles north of Hanoi, or the other positions they have seized along their front inside Vietnam.

The battlefield appeared as stable as it has been for the last two days with artillery duels and skirmishes for the hills without main force troop movements. Information available here on what is happening in the fighting remained very sketchy, however.

In a separate broadcast, Hanoi said its Foreign Ministry sent China a note today rejecting China's latest call for negotiations which Peking issued yesterday. Vietnam consistently has refused to negotiate until all Chinese troops leave Vietnam.

Hanoi mentioned negotiations for the first time in its rejection, but said they could only be held to normalize Sino-Vietnamese relations after a complete and unconditional Chinese withdrawal.

The broadcast said China was following the path of the United States in attacking Vietnam and would be defeated as the United States had been.