Washington: The United States urged Turkey on Saturday to exercise restraint after a failed military coup sparked a government crackdown, and warned its NATO ally that public suggestions of a US role in the plot were ‘utterly false’ and harmful to relations.

President Barack Obama urged parties on all sides of the crisis to avoid destabilizing Turkey and follow the rule of law after the coup attempt against President Tayyip Erdogan.

The coup attempt complicated US-led efforts to combat Islamic State. Turkey closed its airspace to military aircraft and power was cut off to Incirlik air base, which US forces use to launch air attacks against the militant group.

US officials were working with Turkish officials to resume air operations quickly, the Pentagon said.

Secretary of State John Kerry told Turkish Foreign Minister Mevlut Cavusoglu that authorities should respect the rule of law during their probe of the coup.

He also said ‘public insinuations or claims about any role by the United States in the failed coup attempt are utterly false and harmful to our bilateral relations,’ the State Department said.

Turkey has long been a key US ally but relations have been strained in recent years and Erdogan’s government has accused US-based cleric Fethullah Gulen of being behind the coup attempt.

Prime Minister Binali Yildirim said any country that stands by Gulen will be considered at war with Turkey, and Erdogan urged Washington to deport the cleric.

Kerry said the United States was willing to help Turkey as it tries to identify those involved in the coup attempt, but made clear it would only act if there was evidence against Gulen.

‘We fully anticipate that there will be questions raised about Mr Gulen, and obviously we invite the government of Turkey ... to present us with any legitimate evidence that withstands scrutiny and the United States will accept that and look at it and make judgments appropriately,’ he said.

Gulen has condemned the coup attempt and denied any involvement in it.

Obama conferred with his national security and foreign policy advisers on Saturday morning and reiterated his support for the ‘democratically-elected, civilian’ government of Turkey.

‘While we have no indications as of yet that Americans were killed or injured in the violence, the president and his team lamented the loss of life and registered the vital need for all parties in Turkey to act within the rule of law and to avoid actions that would lead to further violence or instability,’ the White House said.

Obama noted the United States needed continued cooperation from Turkey in the fight against terrorism.

Forces loyal to Erdogan largely crushed the last remnants of the coup on Saturday as he launched a purge of the armed forces to tighten his grip on power.

Turkey scrambled jets throughout Friday night to resist the coup launched by a faction within Turkey’s military that saw rebels piloting military aircraft.

The Incirlik air base near Adana in the southeast of the country was running on internal power sources after a loss of commercial power to the base, the Pentagon said.

‘US officials are working with the Turks to resume air operations there as soon as possible,’ said Pentagon spokesman Peter Cook. ‘In the meantime, US Central Command is adjusting flight operations in the counter-ISIL campaign to minimize any effects on the campaign.’

Threat to coalition fight

Erdogan has cooperated with Washington in the fight against Islamic State, but relations have been rocky with US criticism of Erdogan’s increasing authoritarianism, Turkey’s support for Islamist opposition groups fighting Syrian President Bashar al-Assad, and the slow pace in sealing Turkey’s border with Syria to foreign fighters.

The closing of the airspace over Incirlik effectively grounded US aircraft and drones that have been instrumental in the campaign to crush Islamic State in Syria, including supporting drives by Syrian Kurds and moderate Arabs, who are being advised by US special forces, to seize the militant-held city of Manbij and Raqqa, the ‘capital’ of the caliphate declared by Islamic State.

‘Clearly the variable here is how long the closure will last,’ said Jeffrey White, a former senior Defense Intelligence Agency analyst now with the Washington Institute for Near East Policy. ‘If we’re unable to fly from Incirlik, it will have a significant impact on the air campaign.’

A Turkish presidency official in Istanbul said the move was temporary and aimed at preventing rogue aircraft from targeting civilians and government buildings.

‘This is a short-term measure which won’t have significant effect on coalition operations,’ the official said. ‘We have discussed this measure with our colleagues in Washington as well and they understand our concerns.’

A prolonged closure of Incirlik’s airspace could force the United States to divert aircraft based in the Persian Gulf to the Manbij and Raqqa offensives, constraining the air power available to support Iraqi and US forces involved in operations against Islamic State.

It could also complicate the Pentagon’s ability to resupply and aid US special forces inside Syria.