The presidents of Russia, Afghanistan, Pakistan and Tajikistan are set to hold a quartet meeting in Russia's southern Black Sea resort city of Sochi on August 18, the Kremlin's press service said on Monday. During the summit, Russian President Dmitry Medvedev will hold individual bilateral meetings with Afghan President Hamid Karzai and Pakistani President Asif Ali Zardari. Medvedev will hold a separate bilateral meeting with Tajik President Emomali Rakhmon "later" during his official visit August 18-20, the Kremlin said. No details were given on the agenda of the four leaders.