The announcement appears to be a way for Japan, which is barred from sending troops for combat by its pacifist constitution, to show support for Afghanistan's reconstruction while Obama reviews his options for a new strategy in the conflict.
Prime Minister Yukio Hatoyama's government, which wants to put Tokyo's ties with Washington on more equal footing, doesn't plan to extend Japan's refueling mission in the Indian Ocean when it ends in January, partly because it lacks a mandate from the United Nations. Some members of Hatoyama's party also say the mission violates the country's constitution.
Japanese officials said the aid shouldn't be seen as simple replacement for the refueling mission, but aimed at creating jobs and supporting its development.
"The refueling mission and the $5 billion aid are separate issues," Foreign Minister Katsuya Okada said. "Japan puts emphasis on nonmilitary support. We'll try to explain our principle so we can gain international understanding."
The aid, squeezed out despite Japan's budget constraints, "purely reflects Japan's commitment to fulfill its global responsibility because of the importance of Afghanistan," Okada said.
Japan will give up to $5 billion in aid for Afghanistan over five years, beginning later this year. The funds are to be used in areas such as building up the police force and on agriculture and other infrastructure projects. In April, Japan had also pledged $1 billion in aid to Pakistan.
"It is our hope that the governments of Afghanistan and Pakistan, while effectively putting this support from our country to use, will strive for reforms in anti-terrorism and their domestic economies," Chief Cabinet Secretary Hirofumi Hirano told reporters.
The Japanese self-defense force deployed a 600-strong force to southern Iraq in early 2004 on a humanitarian mission that ended in 2006.
Since 2002, Tokyo has provided nearly $2 billion for Afghanistan, including six months of salaries for 80,000 Afghan policemen that Tokyo pledged in March.
The news comes even as the U.S. and Japan wrangle over how to carry out a 2006 agreement to reorganize the 47,000 U.S. troops in Japan under a security pact. That topic, as well as climate change and economic issues, will likely be on the agenda when Obama and Hatoyama meet on Friday.
A major sticking point in the U.S. military reorganization plan, agreed to by the previous Liberal Democratic government that lost August elections to Hatoyama's party, has been the future of U.S. Futenma Marine base in Okinawa.
The plan was to relocate it to a less crowded part of the southern island, but some members of Hatoyama's government want it moved off Japanese territory entirely. Some Okinawan residents have complained the bases cause too much noise and crime.
A procession of high-ranking U.S. officials, including Pentagon chief Robert Gates, have visited Tokyo in recent weeks to press for a quick resolution, but officials from both sides say a resolution of Futenma's future isn't going to happen during Obama's Friday meeting with Hatoyama.