Vladimir Putin served two terms as president before standing down
Russian MPs have backed a bill to extend the presidential term from four to six years amid speculation it may herald Vladimir Putin's early return.
The bill was announced only last week by President Dmitry Medvedev and is being fast-tracked through parliament.
Mr Putin became prime minister this year after being obliged under the constitution to step down after two consecutive presidential terms.
But speculation is rife that he is planning to return to the presidency.
The BBC's Richard Galpin says 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 Duma passed the bill in its first reading on Friday by 388 votes to 58.
The bill will have both its second and third readings in the Duma on Wednesday.
It must then be approved by the upper house, the Federation Council, after which regional assemblies will also vote on it - a process likely to continue into December.
There is no doubt the bill will be approved quickly as the Kremlin's party, United Russia, controls all the assemblies.
The constitutional change will only apply to the next president and the government says it is needed because the existing four-year term is too short to implement serious reforms in such a huge country.
One political analyst told the BBC that Mr Putin, who stood down as president in May, could now be planning to come back well before the next election in 2012 and wants a longer term in office.
The word is that Mr Putin wants to be able to deal with the financial crisis, which is beginning to hit Russia very hard, our correspondent reports.
Speaking earlier this week, Mr Putin denied the bill was tailor-made to bring him back to office, saying the legislation was aimed at "fostering the development of democracy" in Russia and had "no personal dimension".
He pointed out that in Finland, for example, the presidential term was also six years. In France, up until 2002, it was seven.
"As for who will run for office and when, it's too early to talk about that now," he added.
The Communist opposition in the Duma attempted unsuccessfully to have the constitutional amendments bill removed from the agenda, arguing that there was no reason to make the changes now, given that the next election was not until 2012.
Russia's constitution bars a president from serving more than two terms consecutively, but Mr Putin could be re-elected for a third term after his protege Mr Medvedev.
Vladimir Ryzhkov, a commentator and former opposition MP, theorised in a newspaper article on Friday how Mr Putin, who is still a hugely popular figure in Russia, could return to the Kremlin early.
"Using pretexts such as the new constitution and the need to strengthen the state in the face of the crisis, he might announce through Medvedev snap presidential and parliamentary elections as early as March or April," he wrote in the Moscow Times.