Vladimir Putin served two terms as president before standing down
A bill to extend the presidential term from four to six years has been backed by Russia's upper house of parliament after regional assemblies endorsed it.
All the Federation Council senators present backed the assemblies' decision to lengthen the term, the last step in the legislative approval process.
Last month, both the lower house and upper house approved the bill.
The bill's rapid progression is being seen as a sign Vladimir Putin may return to the presidency soon.
The changes needed the backing of at least two-thirds of the country's regional legislatures but were approved unanimously, according to Russian news agencies.
The amendment will become law once it is signed by President Dmitry Medvedev but will only take effect after the next presidential election.
Mr Putin became prime minister this year after being obliged under the constitution to step down after two consecutive presidential terms. He was succeeded as president by Mr Medvedev.
Anaylsts say it has always been assumed that Mr Putin may return after Mr Medvedev has completed one term.
But the apparent rush to get this constitutional amendment through is being seen by some as a sign that Mr Putin is in a hurry and may return much sooner.
Then he could potentially serve another two six-year terms.
The bill also extends the mandate of the lower house, the State Duma, from four years to five.
The government says the constitutional changes are needed because the existing four-year term is too short to implement serious reforms in such a huge and complex country.