By Maria Tsvetkova and Elizabeth Piper
MOSCOW (Reuters) - More than 40,000 Russians have signed up to protest in Moscow on Saturday against a disputed election, dismissing Kremlin promises of political change that could ease Vladimir Putin's grip on power.
The rally follows protests by tens of thousands of people across Russia on December 10 and is intended to pile pressure on the prime minister, who has responded with only minor concessions and seems confident of winning a presidential poll in March.
Bringing together liberals, nationalists, anarchists, environmentalists and urban youth, protest organizers have sometimes struggled to agree on how to proceed, holding long debates over who should speak or who should lead the movement.
They eventually settled on a list of 19 speakers that includes former Soviet President Mikhail Gorbachev, anti-corruption blogger Alexei Navalny, rock singer Yuri Shevchuk and writer Boris Akunin.
Their message is clear. The outcome of an online vote on what slogans to put on 2,000 balloons at the rally was definitive: "You don't represent us!" was the most popular, followed by "You swindled us!" and "We will not stop!."
"I am absolutely sure that up to 1 million people are ready to take part in such rallies ... I see the people's mood," said Navalny, who coined the phrase 'the party of swindlers and thieves to describe Putin's ruling United Russia party.
"They stole about 1 million votes. And that's only in Moscow. I think that these people are completely dissatisfied with what happened and are ready to defend their rights, including going out on to the streets," he told Reuters.
The opposition has rejected conciliatory efforts by Putin and President Dmitry Medvedev, saying they have ignored their key demand for a rerun of the December 4 parliamentary poll, which handed a slim majority to the ruling United Russia party.
The opposition says United Russia benefited from widespread voting irregularities and international monitors said the vote as slanted in the ruling party's favor.
Medvedev promised on Thursday to relax the Kremlin's grip on power, including measures to restore the election of regional governors and to allow half the seats in the State Duma lower house of parliament to be directly elected in the regions.
On Friday, he sent for parliamentary approval laws to reduce the number of signatures a party needs to launch a presidential candidate and to simplify the process for parties to compete in elections. They are due to go into effect on January 1, 2013.
But opposition leaders said the moves were too little, too late by leader who has carried out few of his reform promises since he was ushered into the presidency by Putin, who was barred by the constitution from a third successive term.
"Medvedev promised us so much ... Now should we not go anywhere? Really? Should we sit quietly and wait until they are fulfilled?" organizers asked sarcastically on their Twitter feed, @WakeUpR, one of several sites where requests have been posted on anything from finding a Father Christmas for the rally to printing banners.
The protesters have permission to stage a rally of 50,000 on Moscow's Sakharov Avenue after their first and second requests for sites near the Kremlin were rejected.
Police, who hardly intervened in the protests two weeks ago, said they would allow protesters to bring thermoses, with weather forecasters predicting the coldest day of winter so far.
But most youth aged between 16 and 18, some of the most active people on Facebook and other social networking sites, will not be able to attend after schools changed the timetable for a citywide mathematics exam.
On Friday, the protest's Facebook site had almost 44,000 people who had pledged to attend the rally, and 9,468 maybes.
Putin's popularity has fallen since he and Medvedev announced plans in September to swap jobs next year, a decision which many Russians said showed a disregard for democracy.
Putin, 59, has suggested that many of those taking part in the biggest protests since he came to power 12 years ago had been paid to turn out. He has blamed the United States for stirring the protests and foreign powers for funding them - a theory that has spread across pro-Putin websites.
The Kremlin's chief political strategist, Vladislav Surkov, continued the argument by suggesting the demonstrators were following a script.
"(Protesters) are acting by the book, following ... new revolutionary methods," said Surkov.
"There are those who want to turn the protests into a color revolution - that is for sure," said the president's first deputy chief of staff in an interview with Kremlin-friendly newspaper, Izvestia, on Friday.
Patriarch Kirill, head of the Russian Orthodox Church, warned Russians not to be corrupted by social networking sites. He told RIA news agency that the information on them made Russians "especially vulnerable to manipulation."
He said political change alone could not transform society, it could only happen with a "metamorphosis of the soul."
(Additional reporting by Thomas Grove, writing by Elizabeth Piper, Editing by Timothy Heritage)