The leaders of the G8 powers were to tell Libyan strongman Moamer Kadhafi on Friday that he has lost all legitimacy and must step down, according to a draft version of their summit statement.
The leaders were still meeting, and it was not immediately clear if they would authorise the strong language in the draft, with Russia in particular keen to promote a negotiated settlement to the Libya civil conflict.
But the language in the draft being circulated among the delegations in the French resort of Deauville early Friday was stark.
"It is clear that Kadhafi and his regime continue to commit grave abuses against the Libyan people. Kadhafi has lost all legitimacy. He must go," the statement said, warning: "These criminal actions will not go unpunished.
"We demand the immediate cessation of the use of force against civilians by Kadhafi's followers and mercenaries as well as the cessation of all incitement to hostility and violence against the civilian population," it said.
A draft statement by G8 leaders seen by AFP on Friday said "we will consider action in the United Nations Security Council" if Syria does not stop using force against protesters.
G8 talks were ongoing in the French resort of Deauville and it was not clear whether the draft's strong language would be kept in the final declaration, with Russia in particular wary of threatening a Middle East ally.
"We call on the Syrian leadership immediately to stop using force and intimidation against the Syrian people and to respond to the legitimate expression of the demands of the Syrian people," the draft said.
"We also call for the release of all political prisoners in Syria... Should the Syrian authorities not heed this call, we will consider action in the United Nations Security Council," it warned.