Japan's Prime Minister Yoshihiko Noda in Tokyo on April 21. (Reuters)

A planned announcement of an agreement on moving U.S. forces out of Okinawa and relocating a Marine air base may not be happening.

Three key Senate Armed Services Committee members said they had concerns and that any agreement would need Senate approval.The State Department says it’s working with the Hill on this.

Obama and Noda have met twice before, once in New York and again in Hawaii, and appear to have a decent relationship.

Noda’s visit is the first by a Japanese prime minister since the spectacular (for Loop Fans, anyway) visit of Yukio Hatoyama during a 36-nation nuclear summit two years ago this month.

We wrote that he was “the biggest loser,” getting only 10 minutes with Obama, because he was “hapless and (in the opinion of some Obama administration officials) increasingly loopy.”

The Japanese media went into overdrive, we noted. Hatoyama, who agreed he may have been “loopy,” resigned June 2 amidst a faltering economy.

We trust Noda’s visit will be more “fruitful and productive,” as the diplos like to say.