U.S. President Joe Biden is set to host Tayyip Erdogan at the White House on May 9 in the Turkish leader’s first bilateral visit to Washington since Donald Trump was president, U.S. and Turkish officials said on Friday.

Ties between the NATO allies, long strained by differences on a range of issues, have thawed since Ankara ratified Sweden’s NATO membership bid in January, following a 20-month delay that had caused frustration in Washington.

Yet strains persist, including over northern Syria, where U.S. forces are allied with Kurdish militants that Ankara deems terrorists and against whom it has conducted cross-border military operations.

Washington meanwhile has pressed Ankara to do more to ensure its sanctions on Russia are not circumvented in Turkey, a littoral Black Sea state along with both Russia and Ukraine.

A U.S. official said Washington sees the meeting as an opportunity for Erdogan to agree a full ban on the transshipment via Turkey of dual-use goods that it says Russia uses in its war effort in Ukraine.

Since Biden was elected in 2020, he and Erdogan have met a few times on the sidelines of international summits and spoken by phone. Turkey has pressed for a meeting at the White House, where in 2019 Erdogan visited Trump, with whom he enjoyed good personal ties.

One of the two Turkish officials who confirmed the planned May visit said the visit was taking place during “a window of opportunity” for bilateral ties.

“We hope the visit will also be an opportunity to deepen cooperation in various areas and consolidate the spirit of alliance, including on counter-terrorism,” the person said, requesting anonymity.

Ankara has complained for years of its deep discomfort with U.S. support for the Syrian Kurdish YPG militia, which it deems a terrorist organisation linked with Kurdish militants waging a decades-old insurgency against the Turkish state. But Washington says the YPG are key allies against Islamic State in Syria.

Despite discord over the U.S. military presence in Syria and U.S. support for Israel in its war with Hamas, Washington and Ankara recently sealed a long-delayed deal for Turkey to purchase U.S. F-16 fighter jets.

The Biden administration is looking to see if it can secure a commitment from Ankara during the visit to impose a ban on designated “dual-use” goods, like chemicals and microchips, to Russia and other countries known as entry points, the U.S. official said.

Washington has already sanctioned several Turkish individuals and companies, including in shipping, for contravening santions. Turkey supports Ukraine but opposes the Western sanctions on Russia, with which it also maintains good ties, but says they will not be circumvented on Turkish soil.

“The U.S. inter-agency remains unconvinced about Turkey’s enforcement,” the official said. “There is stuff they’re turning a blind eye to…they need to go to the companies proactively, and tell them to stop doing business with people that will get them sanctioned.”

The United States and Turkey set up a sanctions working group just before meetings between delegations in Washington earlier this month, during which U.S. Secretary of State Antony Blinken and Turkish Foreign Minister Hakan Fidan got together.

The second Turkish source, a security official, said Turkey’s top intelligence official Ibrahim Kalin was to meet with members of the U.S. House of Representatives for talks on the planned visit and other bilateral issues.

On Thursday and Friday, Fidan and Turkish Defence Minister Yasar Guler also met the U.S. delegation.