A Turkish official on Monday denied reports of an agreement with the United States and Arab allies on using an air base in southern Turkey for operations against the Islamic State group. 

An unnamed official told the Associated Press that there is no new agreement, and Turkey and the U.S. are still talking about the Incirlik air base as well as Turkish demands for the creation of a no-fly zone and a safe haven for refugees. 

The denial comes after Obama administration officials told The New York Times that an American assessment team is expected to arrive in Turkey this week to determine what kind of missions can be flown from the Turkish bases, as well as and iron out the details of a training program for moderate Syrian rebels that also reportedly was agreed on over the weekend. 

U.S. Defense officials, though, told Fox News it is premature to say what the Turks might be agreeing to, though a U.S. military team is slated to head to Turkey later in the week. 

The government in Ankara has come under pressure from Washington to take a greater role in the fight against Islamic State, commonly known as ISIS, amid the bloody battle for the northern Syrian town of Kobani, on the Turkish border. The fighting has forced thousands of Kurdish refugees to flee into Turkey.

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As fighting continued in Kobani Sunday, Secretary of State John Kerry acknowledged the tenuous situation. Speaking in Cairo, Kerry said the defense of Kobani does not define the international counterterrorism strategy.

Islamic State militants have taken parts of Kobani, Kerry indicated, but not all of it. The United Nations has warned of mass casualties if the town falls.

"There will be ups and there will be downs over the next days as there are in any kind of conflict," Kerry said at the conclusion of an international aid conference for the Gaza Strip.

Elaborating on a theme the Obama administration has zeroed in on in recent days, Kerry said the U.S. has been realistic about how quickly it will prevail against the ISIS militants. Officials have spoken of years of counterterrorism efforts ahead.

U.S. and coalition aircraft have been bombarding the territory in and around Kobani for days, launching airstrikes on dozens of locations and taking out militants, weapons and other targets.

U.S. Central Command said warplanes from the United States, Saudi Arabia and the United Arab Emirates launched airstrikes on four locations in Syria on Saturday and Sunday, including three in Kobani that destroyed an ISIS fighting position and staging area.

Beyond the training and bases, there are other issues the U.S. hopes Turkey will agree to. U.S. officials have not said what all of those would be because discussions are continuing.

Earlier Sunday, President Barack Obama's national security adviser, Susan Rice, made clear the U.S. has not asked "the Turks to send ground forces of their own into Syria."

American officials are "continuing to talk to the Turks about other ways that they can play an important role. They are already essential to trying to prevent the flow of foreign fighters" and prevent extremists from exporting oil through Turkey. "So Turkey has many ways it can contribute," Rice told NBC's "Meet the Press."

Hagel spoke by telephone Sunday with his Turkish counterpart, Ismet Yilmaz, and thanked him for his country's willingness to assist in the fight.

Rear Adm. John Kirby, the Pentagon press secretary, said Hagel "noted Turkey's expertise in this area and the responsible manner in which Turkey is handling the other challenges this struggle has placed upon the country, in terms of refugees and border security."

Turkey and other American allies are pressing the U.S. to create a no-fly zone inside Syrian territory, and seeking creation of a secure buffer on the Syrian side of the border with Turkey. A "safe zone" would require Americans and their partners to protect ground territory and patrol the sky.

Hagel has said American leaders are open to discussing a safe zone, but creating one isn't "actively being considered."

Alongside Egyptian Foreign Minister Sameh Shoukry, Kerry said at a news conference in Cairo that Kobani is "one community and it is a tragedy what is happening there."

The primary focus of the fight against the Islamic State group has been in Iraq, where the U.S. is working to help shore up Iraqi Security Forces, who were overrun in many places by the militants. In Syria, the U.S. is starting by going after the extremists' infrastructure and sources of revenue.

In the meantime, Kerry said, the Islamic State group "has the opportunity to take advantage of that particular buildup, as they are doing. But I'd rather have our hand than theirs."

Gen. Martin Dempsey, the chairman of the Joint Chiefs of Staff, has estimated it would require hundreds of U.S. aircraft and cost as much as $1 billion a month to maintain an area in Syria safe from attacks by the Islamic State group and Syria's air force, with no assurance of a change in battlefield momentum toward ending the Syrian civil war.

"Do I anticipate that there could be circumstances in the future where that would be part of the campaign? Yeah," Dempsey told ABC's "This Week."

The Associated Press contributed to this report.

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