"Where the troops are deployed, they are having a positive impact. Expansion of the force will help stabilize the situation, and we stand ready to do what we can to support this."
The African Union now has 3,320 troops in Darfur, including 450 observers and 815 police officers. The number is set to double by the end of September, ultimately reaching 12,000 soldiers.
The conflict in Darfur is one of the worst in Africa, with 180,000 to 300,000 people believed to have been killed. Some 2.4 million have been displaced from their homes, with 200,000 fleeing into neighbouring Chad.
A ceasefire, concluded in April last year, has never been respected.
The G8 foreign ministers -- from Britain, Canada, France, Germany, Italy, Japan, Russia and the United States -- also called for the prosecution of "all those responsible for massive violations of human rights in Sudan".
"We will continue to support the humanitarian effort in Darfur and across Sudan," said Thursday's statement, which was presented to reporters by British Foreign Secretary Jack Straw, who chaired the G8 meeting.
"More will be needed through this year, but only a political solution can create long-term peace and security for Darfur," it said, welcoming the resumption of African Union peace talks in Nigeria's capital Abuja.