WASHINGTON (Kyodo) The planned transfer of U.S. Marines from Okinawa to Guam appears likely to be delayed by differences over a housing project for U.S. personnel and their families, sources close to Japan-U.S. relations said Friday.

Washington and Tokyo have seen the plan to house relocated U.S. Marines and their families fall more than six months behind schedule. This threatens to delay the transfer, which was scheduled to be completed by the end of 2014 by both governments.

The deadlock in the talks to relocate the marines to Guam may also affect the plan to transfer the heliport functions of the U.S. Marine Corps' Futenma Air Station from Ginowan to Nago, both in Okinawa, as the two elements are closely tied by the bilateral agreement.

The process of selecting a contractor for the project to transfer the marines from Okinawa to Guam has been affected by a bilateral gap stemming from differences over interpretations of their agreement, including quality standards for the houses, the sources said.

At one point during the past rounds of talks, the U.S. side proposed using part of the expenses Japan plans to shoulder for the relocation project to help improve military facilities not directly linked to Okinawa-based marines, they said.

The impasse will most likely delay bids by potential contractors, the sources said, noting that it normally takes about 1 1/2 years before the winning bidder is selected and three to four years before a project of that size can be completed.

One source said a delay beyond 2014 appears to have become the "tacit understanding" of officials from both sides.

Under the May 2006 agreement, Japan is to shoulder up to $6.09 billion of the $10.27 billion relocation cost mainly to build houses and improve infrastructure.