WASHINGTON - The Obama administration is weighing the opening of a new front in the air war against the Islamic State in Syria, part of an offensive to push back militants along the western portion of Syria's border with Turkey and create a relatively safe zone for U.S.-backed Syrian rebel forces to move in.

Under the plan, U.S. aircraft flying from Turkey's Incirlik air base would target positions the militants currently hold along the border north of Aleppo, eastward toward the besieged town of Kobani. Turkish special forces would move into the area to assist targeting and help Syrian opposition fighters consolidate their hold on the territory.

President Obama, who has not yet approved the proposal, was briefed on its outline Wednesday.

The plan, which was developed over the last several weeks during extensive meetings between U.S. and Turkish diplomatic and military officials, also was a subject of discussion between Vice President Biden and Turkey's top political leaders during Biden's visit to Istanbul 10 days ago.

The proposal would at least partly address Turkey's long-standing desire for a protected buffer zone inside Syria along the entire 511-mile border, while providing the faltering rebel fighters with a much-needed boost.

In exchange, U.S. access to Incirlik for use of manned warplanes and armed drones throughout Syria would add as many as six hours to the amount of time that individual strike aircraft could spend "on station," locating and reaching targets. Aircraft currently striking Islamic State positions in northern and eastern Syria fly from bases in the Persian Gulf, a distance of about 1,000 miles.

"That access is huge," a U.S. official said. At the same time, having Turkish special forces on the ground inside Syria would provide "more capable folks to help with targeting" for air strikes.