TOKYO (AP) -- A lunar orbiter that Japan had planned to launch this year could face further delays, possibly until next year or later, because of a funding shortfall and problems developing the probe's information-gathering capabilities, Japan's space agency said Wednesday.

The Japan Aerospace Exploration Agency, or JAXA, released a report to a government-run commission explaining expected delays to the launch of the $135 million Lunar-A probe.

Earlier this year, an agency committee said it would be "difficult" for the probe to be launched as scheduled this summer from a space center in southern Japan because some of its thruster valves have been recalled for potential defects by their U.S. manufacturer, Moog Inc.

The agency has set no new date for the repeatedly postponed launch of the probe. Japanese media said a final decision on the launch date is expected in September.

Japan's space program has been plagued by the unreliability of its main H-2A launch vehicle, which has forced the agency to redirect funding and staff away from other projects.

Last year Japan said it was delaying a larger-scale lunar exploration project dubbed Selene from 2005 until 2006 to investigate why an H-2A rocket carrying two Japanese spy satellites veered off course and had to be destroyed by mission controllers in November. Last December, Japan abandoned its troubled mission to Mars after space officials failed in their final effort to put the Nozomi probe back on course to orbit the Red Planet.

The Lunar-A will be blasted into space by the M-5, a smaller Japanese rocket designed for carrying scientific payloads. Plans call for the probe to fire two missile-like instruments called penetrators that will bore into the surface of the moon and study its composition.

Wednesday's report stressed the need to improve the penetrators' data sending equipment and emergency backup systems.

The probe was first scheduled to be launched in 1999 but the date has since be postponed twice, once because of glitches with the batteries that will power the penetrators, according to JAXA's web site.