ISTANBUL, turkey - Secretary of State John Kerry struggled Sunday to convince Turkey's leaders they should promptly restore full diplomatic ties with Israel, two American allies counted on by President Obama to help calm the turbulent Middle East.

But Turkey demanded that Israel first end all commercial restrictions against the Palestinians before the once-close partners could end their estrangement, which stems from an Israeli raid in 2010 on a flotilla bound for the Gaza Strip. Eight Turks and a Turkish-American died.

Obama revived the rapprochement during a visit to Israel last month, and Kerry aimed to firm that up in Istanbul, the first stop in a 10-day trip.

The stakes are high, given that the U.S. sees Turkey and Israel as anchors of stability in a region riven by Syria's civil war, Arab Spring political upheavals and the potential threat posed by Iran's nuclear program.

"We would like to see this relationship that is important to stability in the Middle East and critical to the peace process ... get back on track in its full measure," Kerry said at a news conference with Foreign Minister Ahmet Davutoglu.

Kerry said that meant promises of "compensation be fulfilled, ambassadors be returned and that full relationship be embraced."

He also met with Prime Minister Recep Tayyip Erdogan and then went to Israel.

Obama, before leaving Israel two weeks ago, arranged a telephone conversation between Israeli Prime Minister Benjamin Netanyahu and Erdogan. Netanyahu apologized for the flotilla incident; compensation talks are expected to begin this week.

But Davutoglu suggested that full normalization of ties would probably take some time.

"There is an offense that has been committed and there needs to be accountability," Davutoglu said.

He signaled that Turkey would pursue a "careful" advance toward a complete restoration of relations, with compensation and an end to Israeli trade restrictions on the Gaza Strip as the stumbling blocks.

Fixing the relationship has long been a goal of the Obama administration, and the United States wants significant progress by the time Erdogan visits the White House in mid-May.

The Turks have reveled somewhat in what they view as a diplomatic victory, with billboards in Ankara celebrating Netanyahu's apology and praising Erdogan.

Perhaps seeking to add to his leverage, Erdogan indicated shortly after the call that he was in no hurry to close the deal and pledged to visit the Hamas-controlled Palestinian territory soon.