Turkey and Russia signed an agreement on a loan deal for Moscow to supply Ankara with S-400 surface-to-air missiles, reportedly finalizing the controversial arms sale that has been in the works for more than a year, Hurriyet Daily News reports. Ankara will obtain two S-400 batteries, but the second battery will be optional. The deal is expected to be worth about $2.5 billion. The missile batteries will not be interoperable with NATO’s radar systems.