ISTANBUL (Reuters) - The United States is poised to impose sanctions on Turkey over its acquisition of Russian S-400 air defence systems, a step likely to worsen relations between the two NATO allies that are already strained by a range of disputes. Differences include policy in Syria where both countries have troops, a U.S. court case against a Turkish bank for breaching Iran sanctions, and Turkey’s demand that the United States extradite a cleric it blames for a 2016 coup attempt. MISSILE DEFENCE Turkey’s acquisition and testing of the Russian S-400 ground-to-air defence missiles made Ankara liable to sanctions under U.S. legislation known as Countering America’s Adversaries through Sanctions Act (CAATSA). The United States has said it was suspending Turkey from a programme to produce parts for the Lockheed Martin F-35 stealth fighter jet, the most advanced U.S. warplane, but some production has continued. It has also blocked Turkey’s planned purchase of more than 100 aircraft. SYRIA TENSIONS Turkey is furious about U.S. support in Syria for the Kurdish YPG militia, which Ankara sees as a terrorist group. Turkish forces have carried out three incursions into northern Syria since 2016 to push the YPG back from the border. ADVERTISEMENT Turkey conducted the most recent operation last year despite a warning from U.S. President Donald Trump, who has been broadly supportive of Turkish President Tayyip Erdogan, that he would “totally destroy and obliterate” Turkey’s economy if it went too far. 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 courts would require sufficient evidence to extradite the elderly Gulen, who has denied any involvement in the coup. U.S. CONSULAR DETAINEES An Istanbul court sentenced a local U.S. consulate employee to five years in jail in October for aiding Gulen’s network. Nazmi Mete Canturk, a Turkish security officer at the Istanbul consulate, denied the charges and is free pending appeal. Canturk is the third U.S. consulate worker to be convicted. Hamza Ulucay was sentenced to 4-1/2 years in prison on terrorism charges. Metin Topuz, a translator for the U.S. Drug Enforcement Administration at the consulate in Istanbul, was sentenced in June to nearly nine years in jail for aiding Gulen’s network. ADVERTISEMENT U.S. MIDDLE EAST POLICY Erdogan has condemned the strong U.S. support for Israel. He said the U.S. decision to recognise Jerusalem as Israel’s capital meant Washington had forfeited its role as a mediator in the region. He also criticised Trump’s support for Israeli sovereignty over the Golan Heights, which was captured from Syria in the 1967 Middle East war. HALKBANK In 2018 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. The bank has been indicted on the same charges, and pleaded not guilty to bank fraud, money laundering and conspiracy charges. Atilla was released last year. NEW PRESIDENT President-elect Joe Biden has criticised Erdogan and said the United States should support his political opponents, setting the stage for tensions between the leaders when Biden enters the White House on Jan. 20. Erdogan has said it is too early to comment on the incoming administration. “Let Mr Biden take office. Once he assumes office, we will surely sit down and discuss certain things with Mr Biden,” he told reporters this week. Reporting by Dominic Evans; Editing by Daren Butler and Mark Heinrich