France is ready to stop Islamist militants who control northern Mali if they continue their offensive, French President Francois Hollande has said.
However, Mr Hollande said France would only act under UN authorization.
He was responding to a plea by Malian President Dioncounda Traore for help to counter a renewed rebel offensive.
Earlier, an emergency meeting of the UN Security Council called for the rapid deployment of an African-led international force to Mali.
Islamists captured northern Mali from government forces last April 2012 and have recently claimed further advances.
The UN has approved plans to send some 3,000 African troops to Mali to recapture the north but they are not due to arrive until September.
“They (rebels) are trying to deliver a fatal blow to the very existence of this country,” Mr Hollande said.
“France, like its African partners, cannot accept this. I have decided that France will respond, alongside our African partners, to the request from the Malian authorities.
“We will do it strictly within the framework of the United Nations Security Council resolution. We will be ready to stop the terrorists’ offensive if it continues.”
Earlier this week, the militant Islamist group Ansar Dine said it had entered the key central town of Konna and intended to advance further south.
The army has refused to comment on the claim.