Turkish President Recep Tayyip Erdogan on Wednesday vowed to continue with his offensive against the Kurds in northern Syria until a buffer zone along the country’s border is complete, calling on them to lay down their arms. In a speech to parliament ahead of a meeting with US officials this week, he said he would never negotiate with the Kurds in Syria, viewing their main militia, the YPG, as a terror organisation with links to the Kurdistan Workers’ Party (PKK), which has waged a decades-long war with the Turkish state. The Turkish leader said the only option was for them to relinquish their weapons and allow Turkish and Turkish-backed forces to move into the areas they control and establish a “safe zone”. Russia offered Wednesday to mediate a resolution in northern Syria, further asserting Moscow's role as a regional force. It has moved quickly to entrench its leadership role and fill the void after US President Donald Trump ordered the pullout of American forces. Russian Foreign Minister Sergey Lavrov said in remarks carried by Russian news agencies that Moscow is committed to mediating between Syria and Turkey. Mr Trump, speaking at the White House, said that it was "fine" for Russia to help the Syrian regime. Mr Erdogan has dismissed calls from foreign powers, including the United States, who have demanded a ceasefire in Turkey's week-old operation in northern Syria. "There are some leaders who are trying to mediate... There has never been any such thing in the history of the Turkish republic as the state sitting at the same table with a terror organisation," Mr Erdogan said in a speech to parliament. "Our proposal is that right now, tonight, all the terrorists lay down their arms, their equipment and everything, destroy all their traps and get out of the safe zone that we have designated," he said. This was "the quickest way of solving the problem in Syria," he added. Turkey launched Operation Peace Spring on October 9 with the aim of establishing a "safe zone" across northern Syria, which would push back Kurdish fighters from the Turkish border and allow for the repatriation of Syrian refugees. Mr Erdogan said that once the safe zone was established, "stretching from Manbij to the Iraqi border", then the operation would have "ended on its own". The operation has drawn the ire of Western powers, including the US despite Mr Trump’s apparent greenlighting of the operation. Washington has announced a limited set of sanctions on Turkey and Mr Trump warned he could obliterate Turkey's economy. Several European nations have announced they are halting arms sales to Turkey. But he again appeared to show an unwillingness on Wednesday to stop the unfolding operation that is bringing Turkey and the Russian-backed Syrian army into each other's paths. He said US troops are "largely out" of a region of Syria where Turkish forces are attacking Kurdish fighters. As he met Wednesday with Italy's president, Trump said: "If Syria wants to fight to take back their land, that's up to them and Turkey." Mr Trump added: "There's a lot of sand that they can play with." European powers have warned that the situation could become much worse if Turkey's operation is not halted. Speaking before Syria was discussed in a private session of the Security Council, Germany's permanent representative to the United Nations said the situation on the ground was worsening. "It has not improved. Quite the contrary," Ambassador Christoph Heusgen told reporters. "We do not see how under international law you can determine that the Turkish operation is legitimate." Asked if the council was later likely to issue a statement on Syria, he said: "We'll see. The overarching goal is to have a Security Council with a common view." Russia last week opposed a statement the US had proposed about the Turkish incursion. Russia's top diplomat at the UN, Ambassador Vassily Nebenzia, declined to comment before the council meeting, joking: "Maybe later. My president did not give me permission to speak to you." Mr Erdogan has said that Turkey will not be harmed by any US sanctions. Other top Turkish officials reacted to the US threats. Foreign Minister Mevlut Cavusoglu said Ankara would not be affected by sanctions over its military incursion. In a speech to Parliament on Wednesday, Mr Cavusoglu also said that Turkey would retaliate against sanctions imposed on the country. He said: "No sanctions or threats are acceptable and will not affect our resolve." "We will give the appropriate answer to these sanctions. We will take the necessary steps," he added. US Secretary of State Mike Pompeo on Wednesday said he and Vice President Mike Pence aimed to stop Turkey from pressing on with its assaults in the Syria when the US delegation meets with Mr Erdogan this week. Mr Pompeo, in an interview on Fox Business Network, said the US delegation's goal was to find a resolution to the situation in Syria, not break the US-Turkey relationship. "We have every expectation that we will meet with President Erdogan," Mr Pompeo told the network, adding that it was important that top officials from the Trump administration have direct, "face-to-face" talks. "He needs to stop the incursion into Syria," Mr Pompeo said. "We need them to stand down. We need a ceasefire at which point we can begin to put this all back together again." Asked if he held Mr Erdogan personally responsible for the situation in Syria, Mr Pompeo said: "We have to remember this is a complex situation." The military operation has spawned a humanitarian crisis, with 160,000 civilians taking flight, a security alert over thousands of ISIS fighters abandoned in Kurdish jails, and a political maelstrom at home for Mr Trump, accused by congressional leaders, including fellow Republicans, of betraying loyal US allies, the Kurds. Syrian government forces, backed by Washington's adversaries in Moscow and Tehran, have meanwhile taken advantage of the power vacuum left by retreating US troops to advance swiftly into the largest swath of territory previously outside their grasp.