Francois Hollande on Saturday urged British MPs to back air strikes on Islamic State targets in Syria "in solidarity with France", in a tight vote expected early next week.
British Prime Minister David Cameron on Thursday argued his case to members of parliament for Britain to join air strikes on the jihadist group in Syria, amid signs that opposition was weakening after the Paris attacks two weeks ago.
"David Cameron told me that he would consult parliament to take part in strikes in Syria. And win over the House of Commons," French President Hollande told AFP at the Commonwealth summit in Malta.
"I can only call on all British members of parliament, in solidarity with France but, above all, conscious of the fight against terrorism, to approve this intervention."
Cameron told the lower house that Britain should not "wait until an attack takes place here" before acting, adding it was "morally" unacceptable to be "content with outsourcing our security to our allies".
A vote is expected to be held early next week.
While the numbers are tight, MPs look set to approve the move, meaning the first British air strikes on Syria could come within days.
Meanwhile yesterday, Germany offered France Tornado reconnaissance jets, a naval frigate, aerial refuelling and satellite images to back the fight against the Islamic State jihadist group.
German Chancellor Angela Merkel has pledged "very soon" to decide how to help its closest EU ally battle the IS group in Syria.
"In solidarity with France and in a communal spirit of fighting against terrorism, I can only approve what the British prime minister and the German chancellor have proposed," Hollande said.
"I hope that these two countries will go down this path, taking account of the ties of friendship, taking account of what is at stake in the fight against terrorism.
"There is a Franco-British friendship, there is a Franco-German friendship.
"However, there is also an issue which goes beyond us, because if we have been attacked in France, it's the whole of Europe which has been attacked and it's all the countries which want to preserve liberty which have in fact been attacked."
Before heading to Malta, Hollande attended a solemn ceremony in remembrance of the 130 people killed in the Paris attacks, which were claimed by IS.
Having vowed to crush IS for their role in the attacks, Hollande has spent the week in a whirlwind diplomatic bid to build a broad military coalition.