The Benguela Railroad, once a lifeline of three Central African countries, but closed nearly four years ago because of the Angolan civil war, will be unable to resume its operations across international borders for months yet, according to a visiting Common Market official.

Speaking to reporters at Lusaka airport, Maurice Foley, a senior market official for foreign assistance, cited both "technical" and "security" reasons for the delay.

The line was supposed to resume functioning last November between Angola and Zaire but efforts in this direction never got beyond a formal ceremony marking the reopening of the rail bridge at Dilolo on the Zairian-Angolan border.

Dissidents fighting against the present Angolan government blew up another bridge and swore never to allow the line to operate again until a political settlement is reached.

The Benguela Railroad, over 1,000 miles long, once took about 40 percent of both Zambia's and Zaire's copper exports to the Atlantic port of Lobito in Angola. Its closure in August 1975 because of the Angola civil war provoked a major transportation crisis for Zaire and Zambia, from which neither country has recovered.

Zambia, still facing a major problem in getting out its copper exports, has been sending them through Rhodesia to South African ports since October.

Foley cited among the technical problems still to be resolved the need to repair the entire signal system along the line between Lubumbashi and Dilolo, improved efficiency and more rolling stock for the Zambian railways and beefing up the handling capacity of yards inside Zaire as well as in Lobito.

He said a number of Common Market and other countries were expected to provide loans and technical assistance to get the Benguela line running again. But he gave no indication how much the Common Market would invest in the project or a date when the railroad would resume its operations across borders.

Foley was representing the Common Market at a meeting here of Angolan and Zambian officals who have decided to set up a technical committee to study what repairs are needed and to arrange for foreign assistance.Zaire failed to show up for the first in a series of meetings scheduled between now and late March.

Angola's transport minister, Fernando Muteka, denied during the meeting held in Kitwe in northern Zambia that dissidents belonging to the National Union for the Total Independce of Angola (UNITA), led by Jonas Savimbi, posed any security threat to the line.

"The stories that Dr. Savimbi is controling parts of Angola are false. The security of the line has been guaranteed by the People's Republic of Angola," he was quoted as saying.