(Reuters) - President Tayyip Erdogan called Donald Trump a "friend" in welcoming his return to the White House, and invited him for a visit despite longstanding strains in Turkish-U.S. ties including some rooted in Trump's first term as president.
Here are some of the rifts between Washington and Ankara:
DEFENCE, SANCTIONS, NATO
Turkey, a NATO member and regional military power, angered the Trump Administration in 2019 by purchasing Russian S-400 missile defences. In response, Washington cancelled a planned sale of F-35 fighter jets to Turkey and ousted it from a joint production programme for the planes.
In late 2020, the U.S. House of Representatives approved sanctions on Turkey's defence industry over the S-400s, a package that Trump initially planned to veto but ultimately approved before leaving office.
Turkey has since sought to recoup its $1.6 billion investment in F-35s. Earlier this year, U.S. lawmakers cleared a $23 billion sale of F-16 jets to Turkey - but only after Ankara approved Sweden's NATO membership bid after a 20-month delay that frustrated alliance members.
Sweden and Finland both applied to join NATO after Russia's invasion of Ukraine. Turkey delayed the bids by raising objections over what Ankara said was their protection of groups it deems terrorists.
SYRIA
Turkey's main criticism of U.S. foreign policy has been its support for the Syrian Democratic Forces (SDF), the main U.S. ally against Islamic State in northern Syria for the past decade.
The SDF is spearheaded by a Kurdish group that Ankara says is affiliated with the Kurdistan Workers Party (PKK), which Turkey, the United States and European Union deem a terrorist organisation. Ankara regularly targets the PKK in cross border military strikes in Syria and Iraq.
In 2019, Trump abruptly withdrew U.S. troops supporting the SDF, effectively greenlighting one of Turkey's crossborder operations into Syria.
Around the same time Trump sought to respond to domestic criticism by publishing a letter in which he warned Erdogan against the incursion, telling him not to be a "tough guy" or "fool" and threatening to "obliterate" his economy.
THE PASTOR AND THE LIRA CRASH
A 2018 standoff over Turkey's detention of American pastor Andrew Brunson helped spark the first in a series of lira currency crashes that propelled years of economic turmoil, and a cost-of-living crisis that still lingers with Turkish inflation near 50%.
After Brunson was detained over alleged ties to Kurdish militants and to Fethullah Gulen, leader of an organisation Ankara says launched a failed 2016 coup, Trump's White House imposed sanctions on two government ministers, and then tariffs of 20% on Turkish aluminium and 50% on steel.
Turkey responded by doubling tariffs on U.S. cars to 120% and on alcohol to 140%. But the Turkish lira was already tumbling, driven also by concerns over late interest rate hikes.
Brunson was finally freed and returned to the United States in 2018 after being found guilty by the Turkish authorities of aiding terrorism.
In 2019, Washington ended Turkey's preferential trade status but reduced steel tariffs to 25%, prompting Ankara to lower tariffs on some U.S. imports.
On Thursday, Ankara said it hoped U.S. tariffs on its steel and textiles would fall in Trump's second term.
TURKEY-RUSSIA TIES
Turkey opposed Russia's invasion of Ukraine and has supplied Kyiv with armed drones. But it also irked Western allies by opposing their sanctions on Russia, and it welcomed more Russian tourists and migrants including wealthy business figures seeking safe havens.
Washington has urged Ankara to do more to stop goods flowing to Russia that it says can be used on the battlefield, and has sanctioned several smaller Turkish companies for violating export controls.
Turkish banks, fearing U.S. sanctions, have since clamped down on Russia-related business. Still, Ankara has also said it wants to join the BRICS group of emerging economies to better diversify its trade partners.
Erdogan is alone among NATO leaders in holding regular talks with Russia's leader Vladimir Putin, and he hosted talks between Moscow and Kyiv in 2022, positioning Turkey as a natural facilitator of future peace talks.
Trump has criticised the scale of U.S. support for Ukraine and said that he would end the war within 24 hours as president.