Putin is widely expected to win the election this year. Critics say the election has been set up to ensure his victory.
At a news briefing with six foreign editors, Putin suggested what he will do in six years depends on how well Russia is doing then. A fourth term would give him 24 years as president and prime minister, more than any Soviet leader except Josef Stalin.
Putin, 59, served two terms as president from 2000 to 2008 and then stepped down to become prime minister. Presidential terms have been lengthened to six years.
In the interview with editors from Britain, Canada, France, Germany, Italy and Japan, Putin defended Russia's policy toward the regime of President Bashar Assad in Syria. He accused western countries of fomenting violence by supporting the opposition.
Putin said impossible demands were being put on Assad: "The demand about Assad's forces, that they leave the cities, what is that? And the next demand -- that he put on a wooden overcoat, and music will play in his house, but he won't hear it because they will bury him? He will never agree with those demands."