The split shows the continuing failure to resolve the political stalemate between Mr Siniora’s government and the opposition, which includes Hezbollah.

Efforts to resolve the impasse have not yet borne fruit, and dangerous tensions have been bubbling to the surface.

‘Political blackmail’

Lebanon will have two delegations with two very different views of how to resolve the country’s ongoing political crisis.

President Lahoud argues that as the head of state his is the official delegation to the Arab summit. Anyone else, he says, is just a guest.

But Prime Minister Siniora says it is important that the views of the democratically elected government are represented at the summit as well.

President Lahoud supports opposition demands for a new government of national unity in which the opposition – including Hezbollah – would have the power of veto.

Under Lebanon’s complex sectarian power-sharing agreement, the president believes Mr Siniora’s government has been unconstitutional since the resignation last November of all five Shia ministers.

But the majority in parliament still support the government, which says it will not give in to political blackmail.

Nearly four months after they launched a campaign of protests to force the government’s resignation, some opposition supporters are still camped out in one of Beirut’s central squares and parliament is not meeting.

In Saudi Arabia, Mr Lahoud and Mr Siniora will put their dispute on public display.