ISTANBUL (AP) — Turkey is standing firm against U.S. opposition and expects to take delivery of Russia's S-400 missile defense systems next month, President Recep Tayyip Erdogan said Thursday. Speaking to a group of foreign journalists, Erdogan reiterated that the deal with Russia was sealed and there would be no turning back despite vociferous U.S. opposition. He denied that Washington offered Turkey an "appropriate" deal that would allow it to purchase U.S. Patriot systems instead. "This business is finished for us and for Russia," Erdogan said. "The training of personnel has been completed ... I believe that in the first 15 (days) of next month, the delivery will take place." Turkey's decision to purchase the Russian system has driven a wedge between the two NATO allies. The United States says the Russian system is incompatible with NATO equipment and poses a risk to its F-35 fighter jet program. It has warned that Turkey would be excluded from the F-35 program and could face sanctions. Erdogan, scheduled to meet President Donald Trump during a Group of 20 meeting in Japan next week, said he hopes to dissuade the U.S. from imposing sanctions. The U.S., he said, wouldn't want to lose an ally like Turkey, adding that he would back counter measures against any U.S. sanction. "Our (close) relations with Trump are different to those we have with his subordinates," Erdogan said. "Therefore, I don't deem that these sanctions and things are likely." "Turkey isn't an ordinary country. I am sure that the United States will be very careful when it takes such a step, when considering that our strategic partnership goes back decades," he added. Erdogan did not elaborate on the counter-measures Turkey could take. Some commentators have suggested that Turkey could bar U.S. jets from using the key air base of Incirlik, in southern Turkey. Asked whether Turkey would be excluded from the NATO alliance, Erdogan responded: "The United States does not have the authority to throw out any NATO member from NATO." __ Associated Press writer Suzan Fraser in Ankara, Turkey contributed.