Turkish President Recep Tayyip Erdogan holds his first meeting with President Joe Biden next week, overshadowed by bitter disputes and the US president's cool tone towards Ankara.
Mr Erdogan had to wait three months after Mr Biden's inauguration for their first contact, a phone call in April when Mr Biden said he would recognise the 1915 massacres of Armenians in what is now Turkey as genocide, infuriating Ankara.
For the Turkish president who relied on a close personal relationship with Donald Trump to iron out crises, the more critical and distanced approach from the White House has been a source of frustration.
President Erdogan slams Biden after Armenian Genocide recognition
In Monday's meeting in Brussels they will address disputes ranging from Turkey's purchase of Russian arms to US support for Syrian fighters who are regarded as terrorists by Ankara.
Mr Erdogan said ties with the Biden White House have been more strained than with any US president of the past 20 years.
"We will of course ask him why US-Turkey relations are at a tense stage," he said this month.
Mr Erdogan said he worked with three previous US presidents and "did not experience such a tension with them".
Topping the list of disagreements at their talks on the sidelines of a Nato summit will be Turkey's purchase of Russian S-400 air defence batteries.
Washington says the S-400s would compromise the defences of US stealth F-35 jets if used alongside them.
It has thrown Turkey off the F-35 fighter jet programme, cancelled Ankara's order for 100 planes and is looking to replace Turkish companies that had been making parts for the jets.
Turkey wants more than $1 billion in compensation.
The US has also imposed sanctions on Turkish defence industry officials over the S-400 deal.
Turkish officials say they will keep the air defence missile equipment and have called for a joint examination.
"It is not possible to take a step back on these matters that are Turkey's national security issues," one senior official said.
That leaves little prospect of a breakthrough, even though the two sides have kept talking.
"Turkey wants to negotiate how it could use the S-400s, whereas the Americans want to negotiate how Turkey can get rid of the S-400s," said Ozgur Unluhisarcikli, director of the German Marshall Fund research group in Ankara.
"Which means there is no common base for negotiations."
Afghanistan plan challenged
The Biden administration has increased criticism of Turkey's human rights record, seeking the release of businessman Osman Kavala, who has been detained for three years while on trial in connection with 2013 anti-government protests.
Critics say the case is emblematic of Turkey's crackdown on dissent.
The response from Mr Erdogan has been muted, in part because he is anxious to attract US investment to rebuild economic growth, which has been battered by the global Covid-19 pandemic and a slumping currency.
Mr Erdogan hoped to show a central Turkish role in the Nato alliance in Afghanistan, where Ankara offered to guard and operate Kabul airport to secure access to the country after the US-prompted Nato withdrawal.
That plan may be cut off by a challenge from the Taliban who, after two decades of fighting western-led troops, say Turkey must leave along with other Nato forces.
"At best, co-operation on Afghanistan can help maintain the illusion of a positive agenda," said Nicholas Danforth, of the Hellenic Foundation for European and Foreign Policy.
Mr Danforth said it would help their "dysfunctional relationship" to continue.
But there are some areas of common ground, including attempts to reach a political solution in Libya and opposition to President Bashar Al Assad in Syria.
The Turkish lira firmed on Friday on hopes of progress at the talks, where Ankara will propose reviving joint dialogue groups with Washington.
"Why shouldn't a nice period with Biden start at the Nato summit?" asked a senior official at Turkey's presidency.
"Will it be an easy meeting? Not very much, but nobody is without hope either."
