What can the Commonwealth do?

Mr McKinnon at Harare airport with the Permanent Secretary for Foreign Affairs, Machivenyika Mapuranga

The Commonwealth does not pretend to have powers to coerce members to follow its advice.

It prefers to solve problems by persuasion - the approach Commonwealth Secretary-General Don McKinnon has said he will take in Zimbabwe.

"I am pleased to have the opportunity to have these discussions with President [Robert] Mugabe. I hope they will help towards creating an environment conducive to orderly, free and fair elections," he said in a statement before his departure.

The statement said Mr McKinnon would "express the Commonwealth's concerns" regarding the development of the last two months.

Observers

The Commonwealth Observer Group for Zimbabwe's parliamentary elections will also serve as a form of pressure on the country to hold a democratic election campaign.

General Abubakar: Led Nigeria's return to democracy

Mr McKinnon said his main goal was to prepare the ground for these observers, who will be headed by the former Nigerian head of state, General Abdulsalami Abubakar.

The two men have contrasting experience of the Commonwealth's ability to encourage adherence to its standards on good government and democracy - standards that were summed up in the Harare Declaration of 1991.

As deputy chairman of the Commonwealth Ministerial Action Group (CMAG) in the 1990s, Mr McKinnon took a prominent role in dealing with Nigeria during its suspension from the Commonwealth between November 1995 and May 1998.

And it was General Abubakar who led Nigeria back into the Commonwealth by organising its return to civilian government.

Sanctions

Suspension is not currently an option the Commonwealth is considering in relation to Zimbabwe.

Robert Mugabe: Not yet facing suspension

At a CMAG meeting in London earlier this month UK Foreign Secretary, Robin Cook, ruled out both suspension and economic sanctions - though he indicated that could change if President Mugabe failed to hold elections.

Nigeria's suspension occurred after the death sentences passed on the writer Ken Saro-Wiwa and a group of fellow activists from the Ogoni area, in the Niger delta, in 1995.

The Commonwealth drew up plans for sanctions against Nigeria - including an arms embargo and a ban on sporting links - but they were never put into effect.

Plans for a complete oil and air embargo, and a freezing of leaders' financial assets, were also considered.

Isolation

Two other countries suspended from the Commonwealth in recent years are Sierra Leone and Pakistan.

The suspension of Sierra Leone was a response to the coup against President Ahmad Tejan Kabbah in 1997, and the country was readmitted after Mr Kabbah was restored to power in July 1998.

Pakistan was suspended after last October's military coup.

The Commonwealth has halted some forms of financial assistance to Pakistan, called for the release of members of the former government, and demanded a timetable for the return to civilian rule.

Diplomats have hinted that Pakistan will face expulsion if the military rulers do not give up power within two years, and talked about unspecified "tougher measures".

Suspension from the Commonwealth is a largely symbolic gesture, but correspondents say that suspended countries tend to be keen to end their isolation.

In Africa the organisation still enjoys considerable standing. South Africa has recently rejoined, and two countries - Cameroon and Mozambique - have joined for the first time.