(Bloomberg) -- As the world begins to position for Joe Biden’s move into the White House, few leaders are moving as quickly as Recep Tayyip Erdogan with the next four years looking set to be more difficult to navigate than the last.Turkey’s president and his advisers know the former U.S. vice president well, but that isn’t necessarily a plus with American sanctions against Turkey ready to deploy and held back to date only by Donald Trump.By the time Biden left office in 2017, he had overseen a collapse in relations from close partnership to mutual distrust. In an interview with the New York Times published in January, he called Erdogan an “autocrat” and said the U.S. should back opponents to oust him at the ballot box. “He has to pay a price.”That price could be significant. As well as the threat of sanctions, potentially heavy penalties hang over a Turkish state bank. There are also unresolved differences over the status of Kurdish fighters in Syria, Turkey’s maritime claims in the Mediterranean and other areas.Concern over what could come next may help to explain the Turkish leader’s decision to congratulate Biden and accept his victory in contrast to other strongmen who have benefited from Trump’s tenure, such as Brazil’s Jair Bolsonaro or Russia’s Vladimir Putin.Ahead of last weekend’s virtual Group of 20 video summit, Erdogan spoke in a phone call with Saudi host King Salman. Both countries have angered Washington’s foreign policy establishment, but enjoyed protection from Trump.In a speech on Saturday, Erdogan pushed back against the idea that Turkey’s recent befriending of Russia was “an alternative to our long-established ties with America.” And on Sunday, he called for closer cooperation with Europe, with which he’s been sparring for months.Erdogan was able to do as he liked for four years because he had a friend in the White House, said a foreign policy aide to a Democratic Party senator. That will change with an administration that will take a more “responsible” approach to the Turkish president, the person said.The last few years have seen Erdogan adopt a much more assertive foreign policy that racked up successes in Syria, Libya and most recently Azerbaijan, often at the expense of stronger powers. He even tried taking on financial markets, pressuring Turkey’s central bank to keep interest rates low and pumping credit into the economy long before Covid-19 struck.To Read More: Turkey’s War Against the MarketsThe next American leadership is taking shape. Biden intends to nominate Antony Blinken, his national security adviser when he was vice president under Barack Obama, as secretary of state. Yet just how differently a Biden administration would in reality treat Turkey is unknown.A spokesperson for the transition team declined to comment on plans for Turkey, saying Biden believed in the principle that U.S. foreign policy should be run by one president at a time.Erdogan appears to be preparing for the worst. Turkey’s parliament approved legislation on Thursday to repatriate Turkish energy and mining companies established abroad. A Turkish Energy Ministry official said the move aimed to guard against the impact of potential sanctions.On Nov. 7, the day Biden’s election victory was called, Erdogan fired his central bank chief and switched to less risky monetary and fiscal policies. The timing may have been coincidence, given that a correction was overdue to avoid a looming financial crisis. Still, it will also help make the economy more resistant to shocks.The bank’s new governor raised interest rates sharply, stabilizing the lira. On Tuesday, Turkey took another step toward more orthodox economic management by abolishing a rule that forced lenders to extend credit and buy government debt.Those shocks could now come rapidly. Erdogan’s 2019 decision to take delivery of the S-400 surface-to-air missile defense systems from Russia is subject to sanctions mandated by Congress.Trump “doesn’t want to sanction Turkey and that’s perfectly clear,” said former National Security Adviser John Bolton. “He buys the Erdogan argument that Obama prevented Turkey from buying Patriots and he had no choice but to buy the S-400, which is a crock.”Biden, vice president at the time of the Patriot talks, is unlikely to adopt that line. An amendment wending its way through Congress would in any case force the president to choose a minimum of five sanctions to impose on Turkey from a menu of 12. Options range from the symbolic to the crippling exclusion of sanctioned entities from all financial transactions under U.S. jurisdiction.Then there’s a court case against Turkey’s state-owned Turkiye Halk Bankasi AS. The bank was indicted last year for alleged fraud and money laundering in the course of helping Iran evade U.S. sanctions to the tune of $20 billion. In June, Trump forced the resignation of the lead prosecutor in the case. Halkbank denies the charges and the case goes to trial in March, two months after Biden’s inauguration.EU leaders, meanwhile, will again in December discuss calls from Greece and Cyprus—strongly backed by France—to sanction Turkey over its energy exploration in waters they claim in the Eastern Mediterranean.“I am sure that President Biden will contribute to the restoration of collective security balances in our sensitive region, a region that he knows well as he’s been following it for decades,” Greek Prime Minister Kyriakos Mitsotakis said on Nov. 11 after a meeting in Athens with Egyptian President Abdel Fattah El-Sisi, another Erdogan critic.Turkish officials say they got little from Trump—in particular, failing to extradite Fetullah Gulen, the faith leader Turkey accuses of heading a failed coup attempt in 2016. And there are signs that Erdogan’s White House protection may already be ebbing.Secretary of State Michael Pompeo briefly met with French President Emmanuel Macron, a bitter Erdogan critic, in Paris last week and called on the U.S. and Europe to join in countering Turkey’s recent “aggressive” actions in the region. Visiting Turkey afterward, Pompeo didn’t travel to Ankara to meet Erdogan.Turkish officials say they see Syria as the most important potential challenge for Biden, who said during the election campaign he favored keeping U.S. special forces there. Trump withdrew some of those in 2019 and made way for Turkish troops to clear the border areas of Kurdish fighters that it sees as terrorists, but are U.S. allies in the fight against Islamic State.There’s no obvious solution to some U.S.-Turkish disputes, and there may be limits to how far Erdogan can go in making compromises, even if he wants to. The government of Turkey’s ruling AK Party rests on a coalition with the nationalist MHP party, which would likely resist any concessions to the U.S.“We’re not supporters of Biden or in love with Trump,” MHP leader Devlet Bahceli said in a recent speech. “We await prepared—in caution and suspicion.”(An earlier version of this story corrected the attribution in the eighth paragraph.)(Adds Turkish banking regulator in 14th paragraph.)For more articles like this, please visit us at bloomberg.comSubscribe now to stay ahead with the most trusted business news source.©2020 Bloomberg L.P.