ANKARA (Reuters) - Turkey will renew its offer to form a joint working group with the United States to look into the technical aspects of its acquisition of the Russian S-400 defence systems it acquired, once President-elect Joe Biden takes office, Foreign Minister Mevlut Cavusoglu was cited as saying on Friday. Cavusoglu made the comments to reporters on a flight home from Pakistan on Friday. Biden takes over from President Donald Trump on Wednesday. “We will show sincere efforts to improve our ties. We expect the same approach from the Biden administration,” Cavusoglu was cited as saying by broadcaster NTV. “I think it will be a more predictable period in our ties, but we are ready.” Last month, Washington imposed long-anticipated sanctions on Ankara over its acquisition the S-400 defence systems, in a move Turkey called a “grave mistake”. It also removed Turkey, a NATO ally, from its F-35 fighter jet programme over the move. Washington says the S-400s pose a threat to its F-35 fighter jets and to NATO’s broader defence systems. Turkey rejects this, saying S-400s will not be integrated into NATO, and has offered to form a joint working group to examine the conflicting claims. Ankara says its purchase of the S-400s was not a choice, but rather a necessity as it was unable to procure missile defences from other NATO allies with satisfactory conditions. President Tayyip Erdogan said on Friday he hoped positive steps will be taken on Turkey’s role in the F-35 jet programme once Biden takes office.