The selection of Peter Lamb, an 18-year-old of mixed race, as the first nonwhite member of the South African Davis Cup team has been characterized as "politically expedient" and "a nice gesture at best" by Arthur Ashe. It also has done little to placate civil rights leaders opposed to the South African team's appearance in the United States next month.

Lamb, a sophomore at Vanderbilt University in Nashville, where South Africa is scheduled to play the U.S. in the Davis Cup North American Zone finals March 17-19, was one of two juniors named Sunday to the South African squad.

There is virtually no chance that either Lamb or Robbie Venter, a white 17-year-old South African who is a freshman at UCLA, will be named to the four-man playing team to face the U.S. at Vanderbilt's Memorial Gym, but they have been invited to train as part of a seven-man squad with regular team members Ray Moore, Byron Bertram, Bernie Mitton, Bob Hewitt and Frew McMillan.

Lamb's long-rumored selection, hailed as a breakthrough by some and denounced as tokenism by others, came while a four-man delegation from the International Tennis Federation (ITF) is in South Africa to assess that country's rate of progress toward multiracialism in sport.

The delegation's findings will be put in a report to the annual meeting of the ITF in July, and are expected to play a significant role in determining whether or not South Africa is expelled from the ITF and the Davis Cup Nations.

Ashe, a longtime antiapartheid activist who favors South Africa's expulsion from international tennis but supports the position of the U.S. Tennis Association (USTA) that the U.S. should play South Africa as scheduled and work for her ouster through formal channels, said he was not surprised by Lamb's selection.

He pointed out that South Africa nominated Lamb as its official representative in the Wimbledon Junior championships, an invitational event, in 1976. "That was purely political. It was one of the rationales they used for trying to stay in the Davis Cup," Ashe said. "It had no impact at the grass-roots level in South Africa.

"This (Lamb's nomination to the Davis Cup squad) is also, I think, a purely political move. It's politically expedient (at this time)," Ashe, the only world-class black tennis player and a recognized expert on South Africa, told The Washington Post.

"It's a nice gesture, but at the very top . . . It's better than no gesture at all, but that's about the only good I can see in the move," Ashe added.

"There is some progress being made in sports now, no doubt about it. I'm the first to admit that. But apartheid, as we know it, still goes on in South African life," Ashe said.

He also stressed that Lamb is not black by South African definition, but "colored" - of black and white lineage.

"That a ain important delineation that has not been properly brought out in the U.S. media," Ashe said. "In America, Peter Lamb would be looked upon as black, but in South Africa he is 'colored,' and there is a big difference. Life's a little better for you if you're colored.

"Each racial group has its own tennis body there, by law . . . The coloreds and the Asians are now en route to some sort of federated governmental structure with the whites, but the Africans are being left out."

Lamb, a match and business major who plays No. 1 singles for the Vanderbilt varsity, told the Associated Press in Nashville, "I didn't look at things from a political standpoint, I think I was chosen because of my tennis ability primarily, and that is how I look a this - as a fantastic opportunity to further my tennis.

"The thought of turning it down never crossed my mind," he added. "As far as the politics involved, my own idea is to leave politics to the politicians and sports to the sportsmen."

"I am certain that my participation on the South African team will create quite a lot of flak, but I am accustome to that. Wherever I go as a tennis player representing South Africa I have received flak," United Press International quoted Lamb as saying.

Lamb has represented South Africa in several international junior competitions. "For any sportman, I think, the highest opportunity is to play for his country," he told the AP. "I've gone through the whole thing at home. People can't say anything that hasn't been said to me before, as regrads name-calling."

The president of the Nashville chapter of the National Association for the Advancement of Colored People (NAACP), Charles Kimbrough, said yesterday that Lamb's selection would have no effect on plans for massive demonstrations of the U.S.-South Africa matches.

The Coalition for Human Rights in South Africa - an ad hoc affiliation of such influential civil rights groups as the NAACP, National Urban League and the American Committee on Africa - announced two weeks ago that it would bring pressure to bear on the USTA, federal, state and local officials, and the Vanderbilt administration to have the matches canceled.

Failing that, NAACP Executive Director Benjamin Hooks promised "the biggest demonstrations this country has seen since the 1960s" in Nashville. Kimbrough said plans are under way to transport, house and fee 40,000 protestors.

Small demonstrations on the Vanderbilt campus were scheduled to begin today and continue daily through March 19.

(Contributing to this report was Washington Post Foreign Service Johannesburg correspondent Caryle Murphy.)