A draft bill on US military spending is calling for a temporary halt of American weapons sales to Turkey, a key Middle East ally of Washington.

Clauses on Turkey in the annual defence policy bill – released by members of the House of Representatives on Monday – are the latest strain in already-sour relations between the two NATO allies.

The full text of the draft calls for a temporary arms sales ban against Turkey until the secretary of defence submits a report on the worsening US-Turkey relations to related House committees.

The $717bn military bill “prohibits any action to execute delivery of major military equipment to Turkey until the required report is delivered to the specified congressional committees”.

The proposed US National Defense Authorisation Act must go through various steps before becoming law.

Mevlut Cavusoglu, Turkey’s foreign minister, recently told Turkish media the section on arms sales to Turkey in the bill were “wrong, illogical and not suitable” in relations between NATO allies, stressing Ankara would retaliate if the measures are enacted.

“If the US imposes sanctions on us or takes a similar step, Turkey will absolutely retaliate. But we would not want to do that,” Cavusoglu said.

Mensur Akgun, chair of the international relations department at Istanbul Kultur University, said the move would not affect Turkey’s power to acquire weapons it needs, but would bring a new crisis in bilateral ties.

“Turkey has been producing its own weapons more and more as time goes by. Other high-technology weapons that cannot be produced in Turkey can be supplied by other countries. And Turkey is gradually increasing its weapon purchases from Russia,” Akgun told Al Jazeera from Istanbul.

“The effect would be psychological. Already strained trust between the two sides would take a new dive if these measures are enacted. And both sides would pay the price of such a move that harms both countries’ regional interests.”

Turkey seeks to buy 116 F-35 joint strike fighter jets from the US, and is also in talks with Washington to buy Patriot missiles.

Strained relations

In a highly unusual move for a NATO member, Turkey closed a deal with Russia in December to buy the S-400 missile defence system amid increasingly improved relations between the two countries, particularly concerning the Syrian war.

The S-400 surface-to-air missiles are incompatible with NATO systems and the purchase has alarmed various member countries, which warned Turkey of unspecified consequences.

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The US’ proposed defence bill demands an assessment of Turkey’s purchase of the S-400 system from Russia, and the potential effects of such move on bilateral relations.

According to Hall Gardner, co-chair of the international relations department at the American University Paris, US President Donald Trump hopes to ease congressional restrictions on US arms sales to Turkey in the effort to check the sale of Russian S-400s.

“The risk is that the proposed US congressional legislation will further alienate Turkey, turning it not only to European arms firms, but to closer defence ties with both Russia and China,” Gardner told Al Jazeera.

Russia and Iran, which support Syrian President Bashar al-Assad‘s regime, and Turkey, which backs the moderate opposition, have been in close cooperation through the Astana talks, which aim to find a solution to the seven-year-long Syrian conflict.

Also in Syria, Ankara in January launched a military operation into Afrin in the northwest to push out the US-backed Kurdish People’s Protection Units (YPG) fighters near its border despite Washington’s disapproval. Ankara announced in March that its army and rebels it backs secured the region.

US officials condemned the cross-border offensive, arguing it undermined the fight against the Islamic State of Iraq and the Levant group (ISIS, also known as ISIL), which was largely carried out by Kurdish fighters.

Turkey has long been aggravated by the arms and training support the US has given to the Syrian Democratic Forces (SDF), a US-backed umbrella group of fighters formed to fight ISIL and led by the YPG.

Ankara considers the Kurdish Democratic Union Party (PYD) in Syria and its armed wing YPG to be “terrorist groups” with ties to the banned Kurdistan Workers’ Party (PKK).

The decades-long fight between the autonomy-seeking PKK and the Turkish army has killed tens of thousands of people.

Visa disputes

Last October, the US suspended its visa services in Turkey after a consulate employee was arrested in the country. Ankara reciprocated and stopped giving visas on arrival to US citizens.

The Turkish citizen working for the US consulate in Istanbul was accused of having links to the organisation of Fethullah Gulen, an exiled religious leader and businessman based in the US and wanted in Turkey. Ankara accuses Gulen of masterminding the July 2016 coup attempt that killed more than 300 people.

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Washington’s inaction in extraditing Gulen to Turkey has negatively affected bilateral ties and has been repeatedly denounced by President Recep Tayyip Erdogan.

The US and Turkey’s other NATO allies have repeatedly condemned the Turkish government’s mass detentions and purges after the failed coup.

There are US citizens among the people in jail under “terrorism” charges, including pastor Andrew Brunson, the head of a small Protestant church in the western city of Izmir.

The prosecution, in which Brunson faces up to 35 years in prison, has been condemned by Trump.

“Pastor Andrew Brunson, a fine gentleman and Christian leader in the US, is on trial and being persecuted in Turkey for no reason,” Trump said in a tweet. “They call him a spy, but I am more a spy than he is.”

Local and international rights groups accuse the government of using the coup attempt as a pretext to silence opposition in the country.

The government says the moves are in line with the rule of law and aim to remove Gulen’s supporters from state institutions and other parts of society.

“[Through the proposed sanctions] the US Congress hopes to press Erdogan to put an end to his repressive actions inside the county, while also drawing Ankara closer to the US and away from Russia,” Gardner said.

“If the Trump administration cannot soon mediate disputes with Turkey, the consequences of congressional pressures could, however, result in the contrary,” he added, saying Ankara could end up closer to Moscow and Tehran, which are also under US sanctions.

Follow Umut Uras on Twitter: @Um_uras