The first formal contact between Turkish President Tayyip Erdogan and topadvisers to the US president held two weeks after US President Joe Bidentook office.

According to foreign news agency Reuters, Tayyip Erdogan’s chief foreignpolicy adviser Ibrahim Kalın and US national security advisor Jack Sullivandiscussed issues related to Syria, Libya, the Eastern Mediterranean, Cyprusand Nagorno-Karabakh.

According to the report, Ibrahim Kalın told Jack Sullivan that US supportfor Kurdish militia groups in northern Syria and joint efforts to resolvedifferences between the two countries over Turkey’s purchase of a RussianS-400 defence system.

The White House said in a statement that the talks between the twocountries’ top officials focused on the Biden administration’s desire to“build” US-Turkish relations.

Emily Horn, a spokeswoman for the National Security Council, said Sullivanhad “informed the administration of its intention to strengthentransatlantic security through NATO” and expressed concern that Turkeycould acquire a Russian S-400 air missile system. That is why the alliancehas been damaged.

Read also: Attacks on Kurdish strongholds in Syria, US imposes sanctions onTurkey

NATO allies Washington and Ankara are embroiled in controversy overTurkey’s purchase of the Russian-made 400S defence system.

In December, the former Trump administration imposed long-awaited sanctionson Turkey over the issue, which Turkey called a “serious mistake.”

Washington says the S-400s are a threat to modern US F-35 fighter jets andto NATO’s wider defence system.

Turkey has denied the allegations, saying the S-400 would not be integratedinto NATO.

Read more: Significant developments in US-Turkish relations after tensions

Ankara also offered to set up a joint working group to investigateconflicting claims.

Ankara said the purchase of the S400 was not a choice but a necessitybecause it had failed to obtain missile defence from other NATO alliesunder satisfactory conditions.