ANKARA (Reuters) - Turkish officials are questioning the presence of U.S.-led coalition forces at an air base in southern Turkey over what they see as insufficient support for Turkey’s military operations against Islamic State in Syria.

U.S. Air Force (USAF) C-5 Galaxy Outsize Cargo Transport Aircraft lands at Incirlik air base in Adana, Turkey, August 10, 2015. REUTERS/Murad Sezer

President Tayyip Erdogan’s spokesman Ibrahim Kalin said on Thursday there was no need for a “rushed evaluation” on Incirlik, a base used by NATO allies to launch air strikes against Islamic State in neighboring Syria.

But he questioned why the United States, which backs some Kurdish groups against Islamic State in northern Syria, had not lent support to NATO ally Turkey’s latest push to take the Syrian town of al-Bab back from the jihadists.

“In the past month-and-a-half, we have seen and understood that this support was not given at the sufficient level and effectiveness,” Kalin told broadcaster Kanal 24, calling for full support and saying “excuses are not acceptable”.

Turkey has been angered by U.S. policy in Syria, not least by Washington’s support for Kurdish militia fighters it sees as an extension of PKK militants fighting within Turkey, a group the U.S. and Ankara both classify as a terrorist organization.

Kalin said he hoped the administration of U.S. President-elect Donald Trump, who will be sworn in on Jan. 20, would be more attuned to Turkey’s sensitivities.

Deputy Prime Minister Veysi Kaynak said the U.S.-led coalition had only infrequently used Incirlik to join operations by the Turkish military and the Syrian rebels it backs, raising questions among the Turkish population.

“Their presence (in Incirlik) is being questioned by our people and nation, and this issue is on the agenda of the government,” he told broadcaster A Haber.

Turkey launched an incursion into Syria in August to push Islamic State from its borders and prevent Kurdish militia fighters taking ground in their wake.

A U.S. military spokesman said on Wednesday that Washington was in talks with Ankara about future support around al-Bab, the current focus of the Turkish operations.