General Sir Michael Jackson, the head of the British army, on Friday said a brigade could be sent at very short notice.
"If need be, we will be able to go to Sudan," Jackson said. "I suspect we could put a brigade together very quickly indeed."
Asked how many troops that would entail, he said: "Five thousand".
The army chief's comments came a day after Prime Minister Tony Blair denied as "premature" reports that he had drawn up plans to send troops to the troubled western region of Sudan.
Responding to the dismissed reports, Sudanese Foreign Minister Mustafa Usman Ismail had said that Khartoum would withdraw government troops from Darfur if UK sent forces in.
More than 10,000 people have died and around a million people driven away from their homes in Darfur since a revolt against the Khartoum government erupted in February 2003.
UK Foreign Secretary Jack Straw is to visit Sudan next week.