US Secretary of Defense Robert Gates pauses during a news briefing at the Pentagon in Washington September 17, 2009. [Agencies]

TOKYO: Tokyo may not have the money to complete its joint missile defence plans with the United States, Japan's defence minister said on Wednesday.

"The first half of the missile defence plan is complete, but we are considering what to do about the remaining half," a Japanese official quoted Toshimi Kitazawa as telling US Defense Secretary Robert Gates.

Japan's new Democratic Party government, which toppled a long-ruling conservative government in an August election, is trying to slash unnecessary spending and control massive national debt without damaging an already weak economy.

The official did not give details of which parts of the plan might be delayed or cancelled.

Japan's joint ballistic missile defence programme with the United States includes ship-based SM-3 interceptors and land-based PAC-3 interceptors, as well as sensors and joint research to upgrade the system.

Some of Japan's PAC-3 missile interceptors were deployed in April, when Pyongyang conducted what it said was a satellite launch on a flight path over northern Japan.

The Japanese official quoted Gates as saying financial authorities were always strict and adding that the missile defence plan was a wonderful example of success in the US-Japan alliance.

Japan's defence budget has been falling for seven straight years, reaching about 4.7 trillion yen ($51.9 billion) in the year that ended in March and is set for further cutbacks, domestic media say.

The defence ministry has allocated between 100 billion yen and 180 billion yen ($1.10-1.99 billion) a year to the joint missile defense project annually since 2004.