Rep. Howard Wolpe, chairman of the House Foreign Affairs subcommittee on Africa, appealed today to President Reagan to approve the purchase of 400 trucks for famine-struck Ethiopia and Sudan immediately to help transport backed-up relief supplies to the starving.

The Michigan Democrat warned of a new round of famine deaths in Africa if such transportation was not quickly provided with funds Congress appropriated last spring for African famine relief.

Winding up a 19-day tour of Ethiopia, Sudan and Somalia, Wolpe said that great strides in preventing famine deaths had been achieved but that lack of transport to move food and medicines from Red Sea ports threatened to renew the crisis.

"I think there is a false feeling in the world that the problem of the African famine has been solved by the world's relief effort so far," Wolpe said in an interview after arriving here from Somalia. "That is a false sense of optimism."

Wolpe said that although vast amounts of food indeed had been provided to the most seriously affected famine nations, this food still was not reaching many outlying famine areas because of poor road networks and a lack of trucks, drivers and fuel.

"A delay in dealing with this problem is going to cost lives, and such a delay is unecessary," Wolpe said. "The needs have been known for months, and the money is there to meet them. Food without trucks to carry it is meaningless."

Wolpe sent a cable to President Reagan declaring that a "new famine crisis is imminent" and that "thousands face death" before the November harvests made possible by recent rains in the hard-hit drought areas of Africa's Sahel.

He said it was ironic that while recent rains have raised optimism about an eventual break in the drought, they also have aggravated the immediate problems of transporting food to many areas.

Besides 300 trucks for Ethiopia and 100 for Sudan that U.S. Agency for International Development officials requested a month ago, Wolpe urged Reagan to send Sudan six helicopters -- three more than it was promised earlier.

He also urged immediate disbursement of more than $31 million to the Office of the United Nations High Commissioner for Refugees, the International Red Cross, and the International Committee on African Famine Relief, for medicine, food and economic and agricultural projects to allieviate the famine.