Libya's National Transitional Council (NTC) has appointed as new defence minister the local commander whose forces captured Muammar Gaddafi's son at the weekend, an NTC source told Reuters on Tuesday.

Osama Al-Juwali, head of the military council in Zintan, was given the defence job as part of a cabinet line-up in which secularist liberals were dominant and which had no key roles for the Islamists who have been making a bid for power since Gaddafi's fall.

Luis Moreno-Ocampo, prosecutor for the International Criminal Court, was expected to meet NTC officials in Tripoli later on Tuesday to discuss the fate of Saif al-Islam Gaddafi, who was captured in Libya's southern desert.

Three months after an armed revolt ended Muammar Gaddafi's 42-year rule over the oil producing country, Libya's new rulers are dealing with the tricky task of balancing rival regional factions and ideological camps who are jockeying for influence.

The new government line-up -- which will run the country until elections are held -- was agreed at an NTC meeting late on Monday, a source in the council who has seen the list of appointments told Reuters.

However, in an indication of the tensions around the cabinet composition, the source later said some NTC members, after agreeing the appointments, had re-opened the discussions.

There are some people who do not accept some of the names, said the source, who spoke on condition of anonymity. It was not clear which posts were the subject of debate.

In other appointments, Libya's deputy envoy to the United Nations was named as foreign minister, an oil company executive was made oil minister and the finance minister in the outgoing government was re-appointed, the source said.

LOCAL POWERBASE

Juwali is a former officer in the Libyan military whose forces from Zintan played a crucial role in the offensive on Tripoli which ended Gaddafi's rule in August. He had not previously been seen as a contender for the defence job.

But he appeared to have staked a claim to the post after forces under his command on Saturday captured Saif al-Islam, who is wanted for prosecution by the ICC.

The defence minister's role had been coveted by Islamists, who assumed powerful roles in the chaos following Gaddafi's fall after being persecuted for years.

The source said the NTC had agreed to appoint Ibrahim Dabbashi, the deputy U.N. envoy, as foreign minister. He came to prominence soon after Libya's revolt erupted in February, when he broke with Gaddafi and sided with the rebellion.

Ali Tarhouni, an academic in the United States who returned from exile to run the oil and finance portfolio in the anti-Gaddafi rebellion, was made finance minister, the source said, while Hassan Ziglam, an executive in a Libyan oil company, was given the oil minister's portfolio.

The NTC is expected to announce the cabinet line-up officially later on Tuesday.

Speaking on Monday, prime minister-designate Abdurrahim El-Keib said he would pick the best people to steer the country towards democracy rather than those with the most political clout.

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 visiting U.S. ambassador to the United Nations, Susan Rice.

We're working hard to ensure that what we have is something solid, cohesive, capable of doing the job, he said.

Libya's attempts to build new institutions have been overshadowed by tensions between military and regional factions who want to translate their role in ousting Gaddafi into a share of political power.

Those tensions were illustrated by the capture of Saif al-Islam. The fighters from Zintan who seized him on Saturday, instead of taking him to Tripoli, flew him in a cargo plane to their hometown in Libya's Western mountains and are holding him there until the central government is formed.

Libya's caretaker government has said it will try Saif al-Islam inside the country, rather than send him to the international court in The Hague.

The ICC has issued warrants for Saif al-Islam and Abdullah al-Senussi, Gaddafi's former intelligence chief, for crimes against humanity. NTC officials said al-Senussi had also been captured, but there has been no confirmation.

The issue of where the trials will be held has to be resolved through consultations with the Court. In the end, the ICC judges will decide, there are legal standards which will have to be adhered to, Moreno-Ocampo said in a statement.

(Additional reporting by Marie-Louise Gumuchian, Hisham El Dani in Tripoli, Oliver Holmes and Taha Zargoun in Zintan; Writing by Christian Lowe; Editing by)