Turkey’s President Recep Tayyip Erdogan and Russian President Vladimir Putin have discussed <a href="https://www.thenationalnews.com/world/2022/02/18/russia-ukraine-latest-news/" target="_blank">Moscow's war in Ukraine</a> and Ankara’s planned military operations in northern <a href="https://www.thenationalnews.com/tags/syria/" target="_blank">Syria</a>. It comes after <a href="https://www.thenationalnews.com/mena/2022/05/29/turkeys-erdogan-warns-of-new-syrian-operation-against-us-backed-kurds/" target="_blank">Mr Erdogan revealed plans</a> to launch a cross-border incursion against Kurdish militants in Syria to create a 30-kilometre buffer zone. Mr Erdogan told Mr Putin in a phone call late on Monday that the frontier zone was agreed on in 2019 but had not been put in place, the Turkish presidency said. Ankara carried out an operation against the Kurdish group YPG, or People’s Protection Units, in October 2019. Russia, the Syrian regime and the US also have troops in the border region. Turkish officials consider the YPG to be a terrorist group linked to the outlawed Kurdistan Workers’ Party, or PKK, which has waged an insurgency against Turkey since 1984, leading to the deaths of tens of thousands of people. However, the YPG forms the backbone of US-led forces in the fight against ISIS in Syria. The US has not been happy with Turkey’s previous incursions into Syria. Mr Erdogan also told Mr Putin that Turkey was ready to resume a role in ending the war in Ukraine, including taking part in a possible “observation mechanism” between Ukraine, Russia and the UN. Negotiations in Istanbul held in March failed to make any headway but Turkey, which has close ties to both Kyiv and Moscow, has repeatedly put itself forward as a possible mediator. The Turkish president also called for peace in Ukraine as soon as possible and for confidence-building steps to be taken. In Washington, the National Security Council said National Security Adviser Jake Sullivan had called Ibrahim Kalin, chief adviser to Mr Erdogan, on Monday to discuss the two nations’ support for Ukraine, but also to voice caution about actions in Syria. Mr Sullivan “reiterated the importance of refraining from escalation in Syria to preserve existing ceasefire lines and avoid any further destabilisation,” said Adrienne Watson, spokeswoman for the National Security Council. The Turkish official told Mr Sullivan that Ankara wanted to see "concrete steps" on the existence of what it calls "terrorist organisations" in Finland and Sweden before it would consider their Nato bids, Turkey's presidency said. Turkey has objected to the two countries' joining the Western defence alliance on the grounds that they harbour people linked to the Kurdistan Workers Party (PKK) militant group and others it deems terrorists, and because Finland and Sweden halted arms exports to Turkey in 2019. Mr Kalin had told Mr Sullivan that nations seeking to join Nato must "internalise the alliance's values and principles on security and counter-terrorism". "It was emphasised that it is imperative for Sweden and Finland to take concrete steps regarding the terrorist organisations that threaten Turkey's national security," it said. The White House said Mr Sullivan in the call "expressed support for Turkey’s continued direct talks with Sweden and Finland to resolve concerns over their applications for Nato membership, which the US strongly supports." Sweden and Finland have said they condemn terrorism and are open to dialogue. All 30 Nato members must approve plans to enlarge the alliance.