Libya's prime minister-designate finalised his line-up for a cabinet on Monday and remained adamant he would pick the best people to steer the country towards democracy rather than those with the most political clout.

Three months after Muammar Gaddafi fled Tripoli in the face of a revolt against his 42-year rule, Abdurrahim El-Keib said he would name his cabinet on Tuesday, and even though he would ignore regional rivalries, all regions would be represented.

We will use competence as a basic measure and this way we will be able to include all of Libya's regions. You will see, he told a news conference with the U.S. ambassador to the United Nations, Susan Rice.

He added, however, that he still had to discuss the list with the National Transitional Council (NTC), which led the revolt against Gaddafi and has ruled the country since his fall, and their talks dragged into the evening.

Keib, who worked as an academic in the United States during much of Gaddafi's rule, has long said he intends to name a technocratic provisional government. The extent to which he must give in to political reality remains to be seen.

Tensions between various military and regional factions have lingered, as demonstrated by the capture on Saturday of Gaddafi's son Saif al-Islam in the southern desert.

The fighters from the Western Mountains town of Zintan who seized him on Saturday are holding him in their stronghold until the central government is formed. They say it is to ensure his safety -- his father was killed after he was captured by another militia in his hometown of Sirte last month.

The International Committee of the Red Cross said it had asked Libyan authorities to be allowed to see Saif al-Islam in prison and expected the visit to take place soon.

Nine months after the start of the uprising that sparked a civil war and eventually toppled Gaddafi, Keib's cabinet will have the task of rebuilding a country scarred by conflict and by decades of dictatorship that hollowed out many institutions.

It is due to stay in place until the middle of next year, when elections to a constituent assembly should be held.

Probably within a couple of hours or so I will be visiting the NTC to discuss things related to the matter at hand, Keib said at his lunchtime news conference with Rice.

We have decided that tomorrow is the date when we will announce the government but we're working hard to ensure that what we have is something solid, cohesive, capable of doing the job, he added.

DOUBT

Keib went on to cast doubt on whether Gaddafi's former intelligence chief, Abdullah al-Senussi, had indeed been captured on Sunday as was widely believed, saying he needed to verify the information himself before confirming it.

Before I can confirm it to you, I would like to confirm to myself that he was indeed captured. I will not confirm it to you until I am 100 percent sure, he told a news conference.

A spokesman for the NTC said on Sunday local officials in the desert town of Sabha had confirmed Senussi's capture.

When asked about Keib's remarks, a senior NTC commander said Senussi had definitely been captured.

He is in the hands of the Je'fel Fezzan, General Ahmed al-Hamdouni said, using the name of the force he said conducted the mission in the same region in which Saif al-Islam was found.

Keib said Saif al-Islam and Senussi would receive a fair trial in Libya. That could lead to conflict with the Hague-based International Criminal Court, which has indicted both men, along with Gaddafi, for crimes against humanity.

ICC Prosecutor Luis Moreno-Ocampo is due to visit Libya in the coming days.

It is unclear how the West will respond to Libya's insistence that it can try both men rather than hand them over to the ICC in The Hague. At the joint news conference, Rice preferred not to comment on the issue.

France said on Monday it wanted to try Senussi over a 1989 airliner bombing in Niger that killed 170 people including 54 French nationals.

(Additional reporting by Ali Shuaib, Marie-Louise Gumuchian, Hisham El Dani in Tripoli; Oliver Holmes and Taha Zargoun in Zintan; Editing by Alison Williams)