ADDIS ABABA, Ethiopia (AP) _ The factions that ousted the ruling Marxists after years of civil war are to meet Monday amid tight security and even greater confusion to try to establish a new temporary government.

The conference brings together many but not all of the dozens of factions that opposed the regime of former President Mengistu Haile Mariam. Some warred not only against Mengistu but among themselves.

''It's an absolute hodgepodge of initials - the EPRDF, the EPLF, OLF, EPDA, TPMM and on and on,'' a Western diplomat said Sunday. ''I don't know anyone who knows who they all are.''

Dawit Yohannes, who described himself as the sole authorized spokesman for the conference, told reporters he didn't know when the opening session would start, which factions would participate, how many delegates would attend or when the meeting might end.

Most diplomats thought the meeting would last at least a week. ''These people do love to talk,'' said one, who like his colleagues would discuss the situation only if granted anonymity.

Streets for blocks around the conference site and a nearby luxury hotel housing many of the delegates were blocked off. Former rebels, still wearing the ragtag uniforms they had when they stormed into the capital, manned machine gun and guard posts on rooftops and in the streets.

The conference was organized by the Ethiopian People's Revolutionary Democratic Front, or EPRDF, which forced Mengistu to flee Addis Ababa on May 21 and then shot its way into the capital a week later.

It established an interim government that its leader, Meles Zenawi, said would give way to a broader-based provisional government as soon as one could be formed. The new provisional government would rule until democratic, multiparty elections.

Zenawi said the elections could come in a year, maybe two. It presumably would be up to the conferees or the new provisional government to make the final decision.

The other major item on the conference's agenda was the future of Eritrea, the northernmost province of Ethiopia that provides the Horn of Africa nation its only outlets to the Red Sea.

The Eritrean People's Liberation Front, or EPLF, fought a separate but parallel war with Zenawi's coalition against the government in Addis Ababa, but for different reasons. Zenawi's Tigrean-dominated group wanted Mengistu out and itself in; the Eritreans were interested only in their own independence.

Tigre is the province just south of Eritrea.

Although the two groups cooperated in the stuggle against Mengistu, they are wary of each other and their future relationship remains a question.

Both groups stem from Marxist beginnings. Both now say they favor democracy and a free-market economy. But the Eritreans converted long before the Zenawi's group, which is a coalition dominated by the Tigre People's Liberation Front.

As recently as two years ago, the Tigreans were saying they wanted to oust Mengistu and install a government patterned after that of Albania, then the most hard-line Communist regime in eastern Europe. Albania now is moving toward democracy and a market-oriented economy.

The Eritreans said they would attend the conference, but only to discuss their proposal for a U.N.-supervised referendum in Eritrea to decide whether it is to be independent or federated to Ethiopia.

The Eritrean movement, which has its own internal opposition, says it will not participate in a provisional government for all of Ethiopia. It has established its own provisional government in Eritrea.

The conference will be monitored by representatives of the European Community, the Organization of African Unity, several African nations and the United States.