The Reagan administration has "a unique opportunity" to settle Africa's last major remaining colonial issue, Namibia, but it is unclear whether it has the political will to do so, according to the chairman of the House African affairs subcommittee.

Michigan Rep. Howard Wolpe, who heads a congressional delegation of eight Democrats touring Africa, said he is "not sure yet where the soul fo the administration is on Africa," but he hoped the chance would be seized.

Wolpe, who held talks with Prime Minister Robert Mugabe and other Zimbabwean officials during a two-day vist, said in an interview last night that failure on Namibia "will only be an open invitation for expansion of Soviet influence."

At a press conference today before leaving for South Africa, which controls Namibia, he blamed "continued intransigence" for the failure to reach a settlement.

"There is only one real key to the settlement of the Namibian, conflict and that is South Africa," Wolpe said. So, he added, "it becomes important for the United States to put maximum pressure on South Africa."

The United States has taken the lead in a Western effort to-bring independence to the territory also known as Southwest Africa. The administration has also offered concessions to South Africa.

Wolpe called Reagan's move to rescind the Clark amendment, which prohibits U.S. support for South African-supported guerrillas fighting the Marxist government in Angola, "the most damaging" single action so far in U.S. relations with Africa.

"It is unfortuante those kinds of positive initiatives were offered without any quid pro quo," Wolpe said.