ISTANBUL (Reuters) – Turkey is on the verge of facing U.S. sanctions over its decision to buy a Russian S-400 missile defence system, leaving its already soft currency and economy vulnerable.

After a full blown currency crisis last year, the Turkish lira has come under renewed pressure in recent months due in part to fraying diplomatic ties with the United States on a number of fronts:

MISSILE DEFENCE

Washington is concerned about Turkey’s decision to buy Russian S-400 surface-to-air missile batteries, which are not compatible with NATO defences. It has offered U.S. Patriot missiles instead, with an early June deadline for Ankara to decide. The S-400s are due to be delivered in July.

If Ankara accepts delivery of the S-400s it would very likely trigger U.S. sanctions, block delivery of F-35 stealth fighters Turkey has bought, and cut the country out of joint NATO manufacturing of the U.S. jets.

SYRIA TENSIONS

U.S. support in Syria for the Kurdish YPG militia, which Ankara sees as a terrorist organization, infuriates Turkey. The United States is coordinating with Ankara and the YPG to establish a safe zone on Turkey’s southern border. Turkey wants YPG fighters to withdraw from the area to secure its border, and Washington wants guarantees that the U.S.-backed YPG forces which defeated Islamic State will not be harmed.

IRAN OIL

The United States reimposed sanctions on Iran last year, barring countries from importing its oil. In May Washington scrapped a six-month waiver granted to Turkey and seven other big importers in order to step up attempts to isolate Tehran and choke off its oil revenues.

Turkey, which complained but fully complied with the sanctions, is dependent on imports for almost all of its energy needs and Iran is a leading gas and oil supplier.

U.S. CONSULAR DETAINEES

A Turkish court in May refused to release Metin Topuz, a translator and fixer for the U.S. consulate in Istanbul, who will be held at least until his next appearance on June 28.

His arrest in October 2017 led to a diplomatic dispute and suspension of visa services by both countries. Topuz is one of three U.S. consulate employees who have been charged in criminal cases that have been major irritants in the relationship between the NATO allies.

U.S. MIDDLE EAST POLICY

Erdogan has bitterly criticised U.S. support for Israel. He said its decision to recognise Jerusalem as Israel’s capital meant Washington had forfeited its role as a mediator in the region, while President Donald Trump’s support for Israeli sovereignty over the Golan Heights, captured from Syria in a 1967 war, could trigger a crisis.

The Golan Heights have “nothing even remotely to do with Israel…Trump is a bully,” Erdogan said in March.

VENEZUELA

When Trump gave his public backing to Venezuelan opposition leader Juan Guaido earlier this year, Erdogan said he was shocked by the U.S. president’s move, and responded by calling President Nicolas Maduro to tell him: “Stand tall.”

HALKBANK

Last year a U.S. court sentenced Mehmet Hakan Atilla, a Turkish citizen and banker at Turkey’s state-controlled Halkbank, to 32 months in prison after he was convicted of taking part in a scheme to help Iran evade U.S. sanctions.

Washington is also considering a fine against Halkbank.

Federal prosecutors accused Atilla of conspiring with gold trader Reza Zarrab and others to elude U.S. sanctions using fraudulent gold and food transactions. Zarrab pleaded guilty and testified for the prosecutors.

Zarrab described a scheme that he said included bribes to Turkish government officials and that was carried out with the blessing of Erdogan. Erdogan has condemned the case as a political attack on his government.

TURKEY’S FAILED COUP AND EXILED CLERIC

Turkey demands that the United States extradite Islamic cleric Fethullah Gulen, who Ankara has said orchestrated a failed 2016 military coup against Erdogan.

U.S. officials have said the courts would require sufficient evidence to extradite the elderly Gulen, who has denied any involvement in the coup.