Two NATO allies, Türkiye and the United States, can capitalize on a significant momentum in their relations, U.S. Senator Chris Murphy said Wednesday during a visit to Türkiye following its approval of Sweden's NATO membership bid.

Ties between the countries have long been strained by issues ranging from Türkiye's purchase of Russian S-400 missile defense systems to U.S. support for the PKK terrorist group's Syrian offshoot YPG, which occupies chunks of northern Syria close to the Turkish border.

"You definitely feel some real new, purposeful, good feeling in the relationship and we very much felt that in all of our meetings yesterday," Murphy told Reuters in an interview in Istanbul after talks in the capital Ankara with Turkish leaders.

Last week, President Recep Tayyip Erdoğan spoke of a positive trend in relations between the two NATO allies, with the sale of F-16 fighter jets to Türkiye going ahead after ratifying Sweden's NATO accession following 20 months of delay.

Murphy and Senator Jeanne Shaheen met Erdoğan and Foreign Minister Hakan Fidan to express gratitude for Türkiye's support on the issue and to discuss what will come next.

"I think this is a moment of significant momentum for the U.S.-Türkiye partnership," he said, with many issues on which they can try to capitalize in "a complicated alliance that has ups and downs."

Stances on Russia's war

Murphy said Russia and Ukraine topped the agenda in talks, notably the need to work more closely "to make sure that Türkiye doesn't continue as a place where Russia can get around U.S. sanctions."

On Monday, Reuters exclusively reported sources saying that a U.S. threat to impose sanctions on financial firms doing business with Russia had chilled Turkish-Russian trade. Ankara has said it takes measures to avoid being a haven for sanctions to be circumvented.

"We heard a lot of support for an increased partnership. I think the Sweden vote and the F-16 decision will make it easier for us to work more closely together on helping to enforce U.S. sanctions," Murphy said.

He said they discussed some potential new paths forward to formalize work on sanctions coordination.

Murphy said there was also potential to find a path forward on the issue of Türkiye's purchase of the Russian S-400 systems, which prompted Washington to impose sanctions on Türkiye's defense industry in 2020.

The talks in Ankara dealt with the "very delicate topic" of Syria amid long-running tensions over U.S. military support for forces in a coalition including the YPG, which Washington claims is crucial for the fight against Daesh. Ankara has repeatedly demanded that its ally cut its support and partnership with the group.

"This opening in the U.S.-Türkiye relationship gives us a chance to sit down at the table and really honestly talk about whether there is a way to work more closely together in Syria," he said.

Washington considers the PKK a terrorist organization and promised to remove the PKK/YPG from the Turkish border area in a 2019 pact.