SCENARIOS-What do rebel clashes mean for Somalia?

Clashes between rival Islamist rebels in southern Somalia's Kismayu port have raised fears that the fighting could spread to other parts of the country. Skip related content

Western donors have long hoped that al Shabaab hardliners with links to al Qaeda could be isolated by a deal between more moderate Hizbul Islam leaders and the fragile U.N.-backed government, bringing some stability after years of anarchy.

While there is no realistic chance of peace in the short term, here are some possible scenarios:

HIZBUL DEFEAT AL SHABAAB

President Sheikh Sharif Ahmed has been trying to encourage Hizbul leaders, including his former comrade Sheikh Hassan Dahir Aweys, to join his side and isolate their one-time allies in al Shabaab, which Washington accuses of being al Qaeda's proxy in Somalia. But Ahmed has had little success so far.

Hizbul had said it would fight al Shabaab "everywhere" in the country if battles began in Kismayu. Somalia observers are watching to see whether clashes between the two groups break out in the capital Mogadishu, or central and southern districts where they have maintained an uneasy alliance until now.

A victory for Hizbul might make Aweys more conciliatory -- but he would be hungry for a powerful position.

He and Ahmed ran the Islamic Courts Union that ruled Mogadishu and most of southern Somalia for six months in 2006. Aweys has a lot of influence over many of the rebels, but his willingness to work with members of Ahmed's cabinet is unclear.

Aweys also backed suicide attacks on African Union peacekeepers last month, angering some in the international community who might have been willing to accommodate him in the interests of a stable Somalia.

AL SHABAAB TRIUMPH?

An al Shabaab win that cemented its control of the south, including strategic Kismayu, would worry the government and Western donors, which accuse the group of welcoming foreign jihadists -- including al Qaeda suspects wanted over the U.S. embassy bombings in Nairobi and Dar es Salaam in 1998.

In the new areas that fell under its control, it would be expected to impose its own strict version of Sharia law, which has entailed beheadings, stonings and amputations. U.S. military forces might also launch more attacks to kill its leaders.

Al Shabaab hit the main AU headquarters in Mogadishu with twin suicide car bombs on September 17, killing 17 soldiers including the force's deputy commander. Al Shabaab said the attack, which used stolen U.N. cars rigged with explosives, was in revenge for the killing that week of a most wanted Kenyan al Qaeda suspect by U.S. commandos in rebel-held southern Somalia.

If al Shabaab were to defeat Hizbul forces, it would do little in the short term to affect the government's tenuous hold on power as 5,000 African Union troops are still defending key positions in Mogadishu.

But it would boost the insurgents' morale by leaving them as the sole armed opposition to the administration. It may also embolden the rebels to carry out threats to strike in relatively peaceful regions, such as Somaliland.

A GOVERNMENT OFFENSIVE?

Ahmed's administration may be weak and riven by disputes between ministers, but it could take advantage of the clashes between the rebels now and strike at them in Mogadishu.

With the insurgents preoccupied with their battles centred on Kismayu, Somali government forces supported by the AU mission could use the opportunity to deal damaging blows to their bases in the capital. This might disrupt the rebels long enough to reclaim some strategic real estate in the city, but it would no doubt add to the hundreds of thousands of civilians who have fled the fighting.

While AU troops on the ground have been keen to go on the attack, wrangling over how much they can actually do under their current mandate has prevented any major offensives so far.

STALEMATE?

Probably the most likely outcome. Al Shabaab and Hizbul Islam could fight each other to a standstill in Kismayu, with both sides retreating for long enough to call up reinforcements, and neither group making gains they can hold.

Even if the battles spread to other central and southern towns, or the capital, both sets of insurgents are heavily armed and can call up fresh fighters from neighbouring areas.

This would just add to Somalia's death toll of 19,000 killed since the start of 2007, and force more families to join the 1.5 million people already driven from their homes by the conflict.

And it would leave Western nations still scratching their heads about how to lift Somalia out of its violent quagmire.