A government panel chaired by the Democratic Party of Japan (DPJ) Chief Cabinet Secretary Hirofumi Hirano, met on Tuesday evening to discuss alternative sites for the U.S. Marines' Futemma Air Station in Okinawa.

The meeting, held at Prime Minister Yukio Hatoyama's office, came on the back of talks held earlier in the day in Tokyo between senior Japanese and U.S. officials, aimed at deepening the bilateral alliance.

The U.S. officials told their Japanese counterparts that the existing agreement reached in 2006, to relocate the base to Nago, a city in a less populated part of Okinawa, remains the best plan.

"The United States was very clear in our presentation to the Japanese side that we believe that the current plan was the best plan," Kurt Campbell, U.S. assistant secretary of state for East Asian and Pacific affairs, told reporters after the meeting, adding that the United States is "in no way intransigent," and that the U.S. is a "partner" in the process.

Following DPJ Foreign Minister Katsuya Okada remarking on Monday that the Futemma base may have to stay where it is if there is no other option for relocating the site, sparking a bout of dissent from DPJ lawmakers, the ruling coalition's Deputy Chief Cabinet Secretary, Yorihisa Matsuno, maintained that other options may still be on the table.

"Basically, we are considering every possible option with no conditions, including one to continue using the existing base," Matsuno told the press earlier on Tuesday.

The Hirano-led panel this evening debated the merits of visiting the island of Guam, an alternative relocation plan proposed by Social Democratic Party (SDP), one of the DPJ's junior coalition partners, but reaching a cohesive settlement on the issue is running behind schedule.

Alternative plans from the panel were due for ministerial consideration by the end of January, but the deadline has since been extended to the middle of February and multiple sites may be offered as alternatives, if a single relocation site can't be agreed on, sources said.

Ultimately, however, the Japanese premier is expected to make the final decision.

Hatoyama, under increased pressure from the newly appointed Nago mayor in Okinawa -- himself a vocal critic of the base being moved to Nago -- vowed last week that he would not let the Futemma base remain where it is and would pick a new relocation site and conclude negotiations with the United States by the end of May as he has promised.