Wallace Gregson, U.S. assistant secretary of defense for Asian and Pacific security affairs, said Tuesday in Tokyo that adhering to the 2006 bilateral agreement is the only way to proceed on relocating the Futenma military airfield.

Gregson came to Japan to attend the first session of the Japan-U.S. high-level dialogue, attended by Foreign Minister Katsuya Okada, Defense Minister Toshimi Kitazawa and U.S. Ambassador John Roos.

"The U.S. government believes that the current agreement is the only option that can be put into practice," Gregson was quoted as saying by a Foreign Ministry official. "It took 15 years of discussion and the U.S. government as a whole takes this position."

The first meeting of a minister-level "working group" to look into the relocation plan was held Tuesday afternoon at the Foreign Ministry.

Some analysts, however, said that creating the panel was just a way to buy time and avoid criticism that Prime Minister Yukio Hatoyama and President Barack Obama couldn't come to an agreement during their summit in Tokyo last Friday.