Cameron, speaking at the World Economic Forum in Davos, Switzerland, said his government supported the French military intervention in former colony Mali.
"The French are right to act in Mali and I back that action," he said. "But we need to combine a tough security response with an intelligent political response."
The Malian government asked for French support to thwart the advance of foreign and al-Qaida militants.
An al-Qaida attack on an Algerian natural gas facility last week was said to be in response to the French military action. U.S. lawmakers examining a September attack in Libya had suggested al-Qaida elements have spread across much of the region.
"I believe we are in the midst of a long struggle against murderous terrorists and the poisonous ideology that supports them," said Cameron. "To defeat this menace, we've got to be tough, intelligent and patient."
British Foreign Office Minister for Africa Mark Simmonds met with Malian Foreign Minister Tieman Hubert Coulibaly at an African Union meeting to express support for military action.
British forces are providing logistical support for the Malian intervention.