The PAC-3 Patriot missiles are to be delivered to a Japanese military base in March 2007, speeding up the planned development of missiles in the country by at least a year, Kyodo News agency and public broadcaster NHK said.
The reports come a day after the top U.S. commander in the Pacific said Japan and the U.S. planned to work closely to develop a joint missile shield to defend against the threat posed by communist North Korea.
Kyodo, which attributed the report to unidentified sources familiar with U.S.-Japan relations, said Washington offered Tokyo the Patriot missiles in response to a letter from Japan's defense chief, Fukushiro Nukaga, to Defense Secretary Donald Rumsfeld in late July.
Japan's Defense Agency initially planned to develop an unspecified number of missiles in 2008 and 2009 for deployment at Japanese and U.S. bases in the country.
The agency had planned to request a record-high $1.88 billion from the 2007 budget to help cover the cost of the development, Kyodo said. It was unclear how many missiles were planned for domestic production.
But in the latest deal, the agency will request nearly $100 million extra from the 2007 budget to buy missiles made in the U.S., Kyodo and NHK reported. The agency will also request a supplementary budget for the current year to speed up the deployment, Kyodo said.
Sgt. Terence Peck, a spokesman for U.S. Forces Japan, could not immediately confirm the reports. A spokeswoman for Japan's Defense Agency declined to comment.
On Wednesday, Adm. William Fallon of the Hawaii-based U.S. Pacific Command told Japan's foreign minister in Tokyo that the allies should continue to bolster defense cooperation, according to ministry official Hiroyuki Mase.
Fallon's comments came in response to a request from Foreign Minister Taro Aso for stronger cooperation between the two countries after North Korea tested seven missiles last month, Mase said.
Kyodo and NHK did not say if the offer of Patriot missiles was discussed during Fallon's Tokyo visit.
The allies agreed earlier this year to deploy jointly produced advanced Patriot interceptor missiles on American bases in Japan for the first time. The U.S. has about 50,000 troops in bases across Japan under a bilateral security pact.
After the latest North Korean missile tests, Japan slapped sanctions on the communist country and pushed for a punitive U.N. Security Council resolution. Tokyo also sent its top nuclear envoy to South Korea to discuss restarting six-nation talks on the North's nuclear program.