President Reagan is expected to join thousands of veterans here this weekend for a series of commemorative events, reunions and concerts that will be a sequel to the emotionally charged dedication two years ago of the Vietnam Veterans Memorial.

The "Three Fightingmen" statue, a controversial addition completing the memorial, will be unveiled today and dedicated on Sunday, Veterans Day, in a ceremony at which Reagan is expected to speak.

The theme of the weekend, according to organizers of "Salute II," as the ceremonies are being called, will be reconciliation between Vietnam veterans and veterans of other wars.

"I pray we can use this event as a signal to end any remaining division among veterans," said Billy Ray Cameron, the first Vietnam veteran to serve as commander of the Veterans of Foreign Wars, in remarks scheduled for delivery Sunday.

As part of an entertainment program, singer Wayne Newton will return to the Mall tomorrow, a year and a half after former Interior secretary James Watt booked him there to replace the Beach Boys for a July 4th concert. Also appearing at the 11 a.m. concert will be Frankie Valli and the Four Seasons.

On Sunday morning Defense Secretary Caspar Weinberger will lay a wreath at the Tomb of the Unknowns in the traditional Veterans Day ceremony at Arlington National Cemetery.

The Salute II weekend follows by two years the formal dedication of the Vietnam Veterans Memorial, the V-shaped granite wall where 58,022 names of the dead and missing of the Vietnam War are etched. The cathartic events of 1982, in which many veterans of the war in Southeast Asia were reunited, are likely to be echoed here this weekend when about twice as many veterans of all wars are expected to attend.

Many will come who weren't able to attend in 1982, said Richard Weidman, director of government relations for the Vietnam Veterans of America. "A lot of guys who knew about it in 1982 weren't ready," he said. "Everybody is on his own emotional clock."

George Sullivan, the former Army Ranger who conceived Salute II, said a good number of veterans who missed the dedication two years ago saw it on television. "They said, 'I should have been there.' Now they get a second shot at a historic occasion they have a vested interest in," he said.

The unveiling of the "Three Fightingmen" statue by sculptor Frederick Hart this morning will complete the 5-year campaign by organizers of the Vietnam Veterans Memorial Fund to honor those who fought in Vietnam.

The design of the controversial memorial was chosen by a panel of judges in a nationwide competition. Although the memorial was widely praised, it was also criticized for its stark lines and scale, and the newly completed statue was added in response to the criticism.

The statue, a bronze casting seven feet high mounted on a granite base, depicts three soldiers -- a Caucasian, a black and a Hispanic -- peering uncertainly in the direction of the granite wall.

The exact meaning of the statue is open to interpretation, said Jan Scruggs, president of the Vietnam Veterans Memorial Fund.

"The story I like best," he said, "is that these guys are on patrol and all of a sudden they're in the Twilight Zone and they see the memorial with all the names. And they're looking at the wall to see if their own names are there, or if their buddies' names are on it."

Scruggs said the five years of effort by the Vietnam Veterans Memorial Fund has been "hell," but he expressed satisfaction that the task was done. "Now it's part of the establishment," he said. "It was conceived as an anti-establishment thing. We Vietnam vets were going to have to do for ourselves."

After the dedication of the statue on Sunday, the memorial formally will be turned over by the Vietnam Veterans Memorial Fund to the U.S. Department of the Interior, in an exchange between Scruggs and Interior Secretary William Clark.