Nawaz Sharif in Islamabad

The commercial plane carrying former Pakistan prime minister Nawaz Sharif landed in Islamabad a while ago, paving the way for a long confrontation between the exiled politician and Pakistan President Pervez Musharraf.

It is not yet clear however whether Sharif will be detained, deported, or allowed to enter Pakistan unhindered by its military rulers.

Nawaz Sharif was ousted by Musharraf in a coup in 1999, and after some months in jail in Pakistan, struck a deal to leave Pakistan and go into exile in Saudi Arabia. The Pakistan government says that deal required him to stay away from Pakistan for 10 years, while Sharif said the period was five years.

The Pakistan Supreme Court however recently ruled that there was no impediment to Sharif returning to Pakistan. He had the right to return to the country, and the government could not come in his way, the court said.

As Sharif boarded a commercial airline Sunday to go back to Pakistan, with the stated aim of restoring democracy in Pakistan, Musharraf's options appeared limited, and would in any case end in wide-scale civil unrest.

Reports had the President arresting him on arrival, or his being deported back to Saudi Arabia. The authorities in Saudi Arabia said Sunday that they would provide Shariff shelter if he was deported from Pakistan. If Sharif were allowed into Pakistan, without restrictions, he and his supporters were likely to demand the ouster of Musharraf, the reports said.

Musharraf is preparing to try to secure another term in a presidential election by the national and provincial assemblies some time between September 15 and October 15.

A number of Sharif's supporters were arrested over the weekend, indicating that Musharraf was planning to take a tough line on Sharif.

Musharraf is often described by the US as a friend and ally in the war against terror. Osama bin Laden and other key jihadis are said to be in hiding in the border area between Pakistan and Afghanistan.