CRAIOVA, Romania (Reuters) - NATO ally Turkey is not seeking to antagonize the U.S.-led alliance by purchasing Russian S-400 surface-to-air missiles and is in talks with France and Italy to buy similar weapons, NATO Secretary-General Jens Stoltenberg said. Ankara s decision to buy the Russian system has been seen in some Western capitals as a snub to the alliance, given tensions with Moscow over Ukraine and Syria, while the deal raised concern because the weapons cannot be integrated into NATO defense. But Stoltenberg said it was a sovereign decision and that he had talked it through with Turkish President Tayyip Erdogan.  There hasn t been any request from Turkey to integrate the S-400 into NATO air defense system,  Stoltenberg told Reuters in an interview on a Belgian military plane returning from Romania late on Monday.    I spoke with President Erdogan when I met him in September. I said that the kind of capabilities different nations want to acquire is a national decision,  he said of the S-400 system that Turkey has made an advance payment for and hopes to see delivered in 2019.  Stoltenberg stressed that top Turkish officials, as well as Erdogan, had told him Ankara remained a strong NATO ally. That was despite the S-400 issue and a dispute with Germany over Erdogan s arrest of German nationals as part of a mass purge following last July s failed coup bid. Stoltenberg said Ankara was ready to brief its allies in the U.S.-led 29-member bloc on the reasons behind its decision to buy the S-400 system. Erdogan has blamed NATO countries for failing to propose a viable alternative to the long-range Russian missiles, but Stoltenberg said Erdogan was now talking to Paris and Rome for similar systems, a move the alliance chief welcomed.  He told me that Turkey is in dialogue with France and Italy on possible delivery of air defense systems from them ... on top of the S-400,  Stoltenberg said.  Stoltenberg did not give more details but said Turkey was familiar with the so-called SAMP-T missiles developed because Italy had stationed them in Turkey as part of NATO efforts to help protect Ankara from rocket attacks.  Such weapons are designed to protect battlefields and strategic sites such as airports and sea ports against airborne threats, including cruise missiles and aircraft. The SAMP-T system is produced by Italian-French consortium Eurosam, a joint venture between European missile maker MBDA and Thales. Russia uses different technology, as well as know-how that Moscow is unlikely to be willing to share, experts say.  For NATO, the important thing is interoperability,  Stoltenberg said, speaking on his return from the launch of a NATO force aimed at deterring Russia in the Black Sea region.   We encourage, facilitate allies to develop systems, acquire and operate systems together that will reduce costs and strengthen the defense industries within the alliance,  he said. As part of NATO s collective defense pledge, the allies integrate their ships, planes and weapons systems to make them work together, as well as sharing command across the alliance. Some eastern European allies that were once under Soviet rule still rely on Russian-made planes, but integrating Russia s most advanced ground-based missile system would also be highly complicated for political reasons. While Stoltenberg, a former Norwegian prime minister, took up the NATO post three years ago with a more conciliatory tone toward Moscow than his Danish predecessor Anders Fogh Rasmussen, Russia s Crimea annexation in March 2014 had already badly damaged East-West ties. In the latest dispute, Stoltenberg said Moscow had given misleading information about the size of its war games, known as Zapad, or West, last month.  Our assessment so far shows that the scale and geographic scope of the Zapad exercise significantly exceeded what was announced,  he said, although he said so far there were no signs Russia had left behind troops or weapons in Belarus during the exercises, as some Baltic nations had feared. Russia said Zapad involved some 13,000 troops and has accused NATO allies of exaggerating the size of the drills. 