ABUJA (AFP) -- Nigeria's ruling People's Democratic Party (PDP), weakened by internal feuding, meets today in Abuja to choose its presidential candidate for 2007 in place of the incumbent Olusegun Obasanjo.

With his second four-year term is coming to an end, President Obasanjo is constitutionally barred from standing again when Nigerians vote in April.

In the eight years since the party's formation, virtually all its founding fathers, including three national chairmen, have quit. Nigeria's Vice President Atiku Abubakar, one of the few founders to remain, is temporarily suspended.

Analysts therefore see today's convention as a make or break event for the PDP, which, thanks to the sheer size of Nigeria's population, is likely the biggest party in Africa.

Some 30 party members applied for the top job, but a screening committee is thought to be whittling down the final number of contestants.

PDP national deputy chairman Olabode George told reporters that some 5,000 delegates from the country's 36 states would converge in the federal capital to choose the candidate who will compete with some 50 other approved political parties in the poll.

To emerge as his party's presidential candidate, an aspirant must win the votes of 50 percent of the delegates present.

April's vote is set to bring in the first transition from one civilian administration to another in a country with a history of election violence and vote-rigging.

The PDP, which won national elections in 1999 when the military ceded power to civilians, controls 28 of Nigeria's 36 states and has a majority in the national Parliament.

The party was again victorious in 2003 and has promised to win again in 2007.

"We urge all delegates to work toward the success of the national convention of our great party. We have to make the right choice so that our party will remain the party to beat at the election," George said.

Among the presidential hopefuls are several incumbent state governors, including Peter Odili of southern oil-rich Rivers State, Umaru Yar'Adua of northern Katsina State, Donald Duke of southeastern Cross River State and a handful of retired generals: Mohammad Gusau, Muhammadu Buhari, Mike Akhigbe, Buba Marwa and Ebitu Ukiwe.

Another retired general, Ibrahim Badamasi Babangida, better known by his initials IBB, who ran Nigeria from 1985 to 1993, earlier this week withdrew from the PDP primaries, officially to avoid competing against two of his close friends, Gusau and Yar'Adua.

He said that he had given his support to Yar'Adua's candidacy and hinted that he himself might well contest under a different banner.

Yet another one-time party heavyweight who will not contest is Atiku Abubakar, the vice-president who was instrumental in blocking his boss Obasanjo's bid to amend the constitution and run for a third term.

Abubakar was subsequently indicted on corruption charges by the country's anti-graft agency and then suspended from the PDP.

Relations between Obasanjo and Abubakar have soured in recent months, with the two men publicly trading corruption accusations.

The vice president has made it clear that he wishes to run in the election but Obasanjo, who was also one of Nigeria's military rulers (1976-79), has made it equally clear he does not want Abubakar to replace him.

As a result, many observers expect Abubakar to stand for election under the joint ticket of two major opposition parties, the Action Congress (AC) and All Nigeria People's Party (ANPP).