A U.S. Air Force F-16 warplane prepares to land at Incirlik Air Base in southern Turkey in November 2001. (Tarik Tinazay/AFP/Getty Images)

Turkey denied Monday that it has reached any “new agreement” with the United States to allow the use of Incirlik Air Base in southern Turkey for attacks on the Islamic State militant group, despite suggestions from the Obama administration that a deal had been reached.

A statement issued by the office of Prime Minister Ahmet Davutoglu said talks are continuing between Ankara and Washington over whether to permit U.S. forces to use Incirlik in the fight against the Islamic State, a radical al-Qaeda offshoot that has captured parts of Syria and Iraq. However, “there is no new agreement on the Incirlik issue,” the statement said.

“There are requests and expectations and the negotiations continue,” it added.

The Obama administration has been pressing Turkey to allow warplanes to use Incirlik — where the United States bases aircraft under existing NATO agreements — as part of an effort by a U.S.-led coalition to roll back Islamic State gains.

U.S. officials said Sunday that Turkey had agreed to allow the coalition to use Turkish military bases for the fight against the Islamic State and to use Turkish territory as part of a training program for moderate Syrian ­opposition fighters.

“That’s a new commitment and one that we very much welcome,” Susan E. Rice, President Obama’s national security adviser, said on NBC’s “Meet the Press.” “They have said that their facilities inside of Turkey can be used by the coalition forces — American and otherwise — to engage in activities inside of Iraq and Syria.”

Rice did not specify what kind of military activities the United States would be allowed to conduct from Turkish bases to support operations in Syria. A Defense Department planning team is scheduled to travel to Turkey this week to finalize the plans, U.S. officials said.

In a reflection of the sensitivity of the matter, U.S. officials on Monday were reluctant to further address or clarify the issue for fear of irritating the Turks. “We are grateful for steps Turkey is taking to support the coalition, to include training and the use of some facilities,” said a U.S. defense official who spoke on the condition of anonymity.

Turkey has allowed the United States for some time to use Incirlik, located less than 100 miles from the Syrian border, to help with deliveries of humanitarian aid to needy civilians inside Syria. That has not changed, said a Turkish official who spoke on the condition of anonymity in order to discuss sensitive diplomatic issues.

Turkey has also allowed the U.S. Air Force to conduct drone surveillance missions over northern Iraq from Incirlik for years but has drawn the line at arming the drones or permitting the United States to use other aircraft for airstrikes.

Opening up the base for warplanes would make it much easier for the United States to launch strikes against Islamic State fighters in Syria, instead of having to rely on much more distant air bases in the Persian Gulf. It also would represent a powerful signal of Turkey’s willingness to fully engage in the international coalition formed by the United States to fight the militants.

But Turkey has insisted it will not allow attacks from its soil unless the war is also extended to include Syrian President Bashar al-Assad, whom Turkish leaders believe is responsible for creating the conditions that have enabled the extremists to flourish.

“The Assad regime should be the target for a real solution in Syria,” Turkish President Recep Tayyip Erdogan said in an address at Istanbul’s Marmara University on Monday. He also reiterated Turkey’s demands for the imposition of a no-fly zone and the creation of a safe haven in northern Syria, conditions that the United States so far has not accepted.

Turkey did not dispute a statement Sunday by Defense Secretary Chuck Hagel that an agreement has been reached to train moderate Syrian rebels in Turkey, a step that Turkey has long sought. But it was not immediately clear who would train the rebels or precisely where.

Amid the confusion over Incirlik, the Islamic State launched a new offensive to capture the last neighborhoods of the Syrian border town of Kobane that it does not already control.

Bolstered by reinforcements of men and weaponry that arrived overnight, the jihadists launched a wave of up to six suicide bombings against Kurdish positions in the town, pushing the defenders back several blocks and raising fears that the town’s fall could be imminent.

The gains came despite an intensified wave of coalition airstrikes, with the U.S. Central Command reporting that seven took place around Kobane over the previous 24 hours. Fighter jets from Saudi Arabia participated in the strikes alongside U.S. fighters and bombers, according to a Central Command statement.

Witnesses said there were more strikes late Monday, after the statement was issued, but that could not be independently confirmed.

The strikes have helped Kurdish fighters with the People’s Protection Units, or YPG, hold out against the Islamic State onslaught for the past 10 days.

But Kurdish activists expressed fears Monday that the fighters would not be able to survive much longer.

“The airstrikes are continuous, but it doesn’t make any difference,” said Mustafa Abdi, who is monitoring the battle from the Kurdish border. “The situation is getting worse.”

The Central Command said warplanes struck one large and one small Islamic State unit southwest of Kobane, damaged a militant staging location and destroyed a heavy-machine-gun position.

Three airstrikes northeast of Kobane hit an Islamic State unit and buildings, and another strike northwest of the north-central Syrian city of Raqqah, an Islamic State stronghold, struck a militant garrison, the command said.

Up to 200,000 new refugees have fled into Turkey in recent weeks from Kobane, where Kurdish defenders have faced Islamic State attacks from three sides.

William Branigin in Washington contributed to this report.