ISTANBUL, Turkey - Vice President Biden assured Turkey on Saturday that the U.S. plans to strengthen Syrian rebels and ensure a political transition "away from the Assad regime," but he stopped short of committing to the regime change in Damascus demanded by Turkish President Recep Tayyip Erdogan.

On a fence-mending trip to a critical but reluctant ally in the U.S.-led coalition against extremists from the Islamic State, a group also known as ISIS and ISIL, Biden appeared to edge closer to Turkey's position, but not enough to clarify the central ambiguity in U.S. policy.

"On Syria, we discussed not only to deny ISIL a safe haven and roll back and defeat them, but also strengthen the Syrian opposition and ensure a transition away from the Assad regime," Biden said after a four-hour meeting with Erdogan.

Before the meeting, a Turkish official said Ankara sought "a much more comprehensive approach" than Washington to the crisis in Syria and Iraq.

Erdogan took a step back from his own confrontational rhetoric, saying Turkey's relationship with the U.S. is based on mutual trust and benefit and "is stronger than ever." He said Turkey and the U.S. "have a consensus on several regional issues," an apparent reference to rapidly expanding collaboration in Iraq.

Neither Turkey nor the U.S. can claim a consistent position. The U.S., which is talking about expanding training for moderate rebel forces, in fact has been parsimonious about support for fighters now in the field. Its failure to integrate them into its overall strategy contributed to a stinging setback in Idlib province at the hands of al-Qaeda-affiliated rebels this month.

Yet Biden's visit here also brought forth the first signs of policy convergence. Midway through the discussion here, the Turkish government disclosed that it is willing to train and equip Iraqi government forces, a significant shift to support Iraq's new prime minister, Haider Abadi, after years of tension with his predecessor, Nouri al-Maliki.

Biden's visit to Istanbul was his first since the blow-up last month that followed his public criticism of Turkey for "contributing to the rise" of ISIS.