ANKARA, Turkey — An escalating diplomatic crisis between NATO allies Turkey and the United States may risk suspending a $1.5 billion deal between Turkey and Pakistan for the sale of 30 Turkish-made T129 ATAK helicopter gunships.

The T129 is being produced by Turkish Aerospace Industries under license from the Italian-British company AgustaWestland.

“The problem is related with the U.S.-made parts for which TAI will need U.S. export licenses in order to materialize the deal,” a Turkish aerospace official said.

The T129, based on its predecessor A129 Mangusta, is a twin-engine multirole attack helicopter. The T129 is powered by two LHTEC T800-4A turboshaft engines. Each engine can produce 1,014 kilowatts of output power. The T800-4A is an export version of the CTS800 engine. LHTEC is a joint venture between the American firm Honeywell and the British company Rolls-Royce.

“Apparently we shall need U.S. export licenses to go ahead with the T129 deal,” a senior procurement official said. “This is not a technological or financial matter but is purely political at the moment.”

Go face to face with the TAI T129 ATAK helicopter at the Dubai Airshow 2017.

Washington has sanctioned two Turkish ministers, and U.S. President Donald Trump pledged to double tariffs on Turkish steel and aluminium exports to his country. Turkey retaliated by sanctioning two U.S. secretaries, but the row has already sparked a financial crisis in Turkey. The Turkish lira has lost 81.5 percent of its value against the U.S. dollar in the year to Aug. 12.

The row significantly deepened after a Turkish court refused to release a U.S. pastor who had been in jail since 2016 on charges of terrorism and attempted to topple Turkey’s elected government. Pastor Andrew Craig Brunson was later released from jail to house arrest, but U.S. officials are demanding his immediate release and return to his homeland.

The two NATO allies also have been at odds over U.S. support for Kurdish militants fighting the Islamic State group in northern Syria, as well as Turkey’s refusal to follow U.S. sanctions on Iran, and Ankara’s decision to deploy the Russian-made S-400 air and anti-missile defense systems on Turkish soil.

“This is a commercial deal (with Pakistan) with a country that has friendly relations with America. For Washington what matters should be the recipient of the systems, not who produces it and if relations are bumpy with the producer country,” a Turkish defense official said. “Why should the Americans punish Pakistan for their disagreements with Turkey?”

A TAI official said a U.S. embargo on the chopper deal was unlikely because it would also hurt a U.S. company as well as two British companies and one Italian. “These are not enemy producers,” he said. “They are on the ally side. And we (TAI) are not being sanctioned by the U.S. or any other ally country.”

A U.S. diplomat in Ankara refused to comment.

Turkey and Pakistan signed a deal July 13 for 30 T129 ATAK helicopter gunships. Pakistani officials say their own AH-1F Cobra gunships lack the capability to perform adequately over the higher altitudes of the Hindu Kush mountain range separating Afghanistan and Pakistan.

In 2016, Pakistani officials thoroughly tested the T129 and endorsed the deal.

LHTEC’s T129 engine also powers the 12 AH−1Z Viper attack helicopters ordered from the U.S. These are yet to be delivered, and such a timescale remains unclear in view of present U.S.-Pakistani bilateral relations.

To finance one of the country’s largest defense and aerospace export contracts, Turkey offered Pakistan a $1.5 billion credit line in 2017, but the deal’s payment terms are unknown.

“President Trump is not always predictable. … He may wish to punish Turkey by sabotaging such a critical export contract at a time when the Turkish economy is badly ailing. At the same time he may also wish to give a message to the Pakistanis,” according to a European defense attache in Ankara.

Most recently, Congress took another step toward banning the delivery of the F-35 stealth fighter jet to Turkey after the House and Senate agreed to a compromised text to a defense spending bill. The two chambers agreed to prohibit delivery of any F-35s to Turkey until the Pentagon submits a plan that assesses the impact of expelling Turkey from the Joint Strike Fighter program of which Turkey is a partner. The assessment should come within 90 days of the text becoming law.