Russian Foreign Minister Sergey Lavrov said Moscow and Ankara would not be deterred from military co-operation by US sanctions on Turkey for buying a Russian missile defence system. Washington this month punished Turkey for buying Russia's S-400 air defence system, in a rare move against a Nato ally. US Secretary of State Mike Pompeo at the time told Turkish Foreign Minister Mevlut Cavusoglu that the sanctions were meant to stop Russia receiving substantial revenue from the sale. On Tuesday, Mr Cavusoglu visited Moscow for talks with Mr Lavrov. "We have confirmed our mutual intention to develop military ties with Turkey," Mr Lavrov said afterwards. He said Russian President Vladimir Putin appreciated Turkey's determination to "continue co-operation in this area despite continuing illegitimate pressure from Washington". Mr Cavusoglu said the US sanctions against Turkey were "an act of aggression against our country's sovereign rights", and that Ankara would not give in to pressure. "We prefer to solve all issues including that of the S-400 through negotiations," he said. "After introducing the sanctions the US announced it favours dialogue. We've never been against dialogue." Turkey last year took delivery of the $2.5 billion system, defying warnings that such military co-operation was incompatible with the Nato accord. It was told that Russia would be able to improve its targeting of US stealth planes through the system. Although Russia and Turkey are rivals in conflicts including those in Libya and Syria, Mr Putin and Turkish President Recep Tayyip Erdogan seek to maintain good relations. The two countries are jointly monitoring a Russian-mediated truce over the disputed Nagorno-Karabakh region after a six-week war between Armenia and Azerbaijan, in which more than 6,000 died. Tension between the two nations rose over Nagorno-Karabakh while the fighting continued. Russia accused Turkey of sending Syrian mercenaries to battle Armenian troops, as it had done for Libya's Government of National Accord in Tripoli to broad international condemnation. This month, Turkish police briefly arrested two Russian journalists in Istanbul for allegedly filming a drone production unit without permission.