Nearly 2,000 Vietnamese emigres ended a three-day rally here yesterday with an appeal for world cooperation to overthrow the communist government in Hanoi.

"We are not bellicose. We are not declaring a new war. We are merely undertaking a struggle to liberate our people," said Hoang Co Minh, a retired admiral who leads the National United Front for the Liberation of Vietnam.

The front and its National Support Movement for the Resistance in Vietnam, both based in California, are the largest of more than a dozen competing groups of former South Vietnamese who have been working, largely at cross-purposes, for about five years to organize a coordinated resistance campaign.

The gathering here celebrated this group's third anniversary and was a frank effort to get public notice for the cause.

Officials said delegations from most of the front's 96 chapters worldwide were among chanting flag-wavers who paraded six abreast in breezy sunshine from Farragut Square past the White House to George Washington University.

Wearing the traditional purple plaid scarf of the Vietnamese resistance, Hoang told the crowd that the Vietnamese government "affects the balance of power in the world.

"We are appealing to the world to cooperate with us so that we can solve this common problem together," he said.

The front has united 36 resistance groups within Vietnam and has 10,000 "resistance soldiers" here and in Vietnam ready to fight, Hoang claimed. So far, he said, the front "has trained and organized armed propaganda groups and has secretly sent them to work in appropriate areas" in preparation for an eventual rising of the Vietnamese people.

Calling for unity among the estimated 400,000 Vietnamese in the United States, Hoang said, "Supporting a liberation movement is a mandatory duty . . . it is not a charitable act."

Vietnamese-language banners in the parade echoed that theme, according to the loose translation of one provided by a participant:

"It says, 'If you don't speak up while you are in a foreign country, it means you agree with what's going on at home,' " he said.

Other banners, in English, said, "Commies come, freedom's gone" and appealed for an end to abuses of human rights and for support in the liberation effort.

"I don't like it," said Ann Barrett of Fort Thomas, Ky., one of a group of tourists who watched the parade near the White House. "I think the United States has already done enough for them. They're asking too much."

Earlier in the conference, the Vietnamese laid a wreath at the Vietnam Veterans Memorial. They also passed unanimously a nine-point resolution, part of which declared that "the only way to liberate the people of Vietnam from communism will be to eradicate all traces and vestiges of this genocidal plague."