Lawmakers in the Mazhilis, the lower chamber of the Kazakh parliament, appealed to the council in July to set a date for the election. But the council was slow to move on the issue.
Today's decision resolves a debate over two contradictory articles in the Kazakh Constitution. The first, Article 41, stipulates that the duration of a presidential term is seven years. By this measure, Nazarbaev, whose last reelection came in an early vote in January 1999, is due to see his current term expire in January 2006.
The second, Article 94, says presidential elections should take place on the first Sunday of December following the end of a presidential term. This would have put the vote on 3 December 2006 -- nearly a year after the end of Nazarbaev's current term.
Leaders of the pro-Nazarbaev Otan (Motherland) party said the vote should be moved forward to December 2005, to prevent the country from spending 11 months in a kind of presidential limbo. But other officials argue the poll cannot legally be held before Nazarbaev's term expires.
Zharmakhan Tuyakbai, a leader of the opposition movement For a Just Kazakhstan, has said he hopes to run in the upcoming ballot. He told RFE/RL's Kazakh Service last month that political maneuvering in the Mazhilis and Constitutional Council -- both of which are largely pro-Nazarbaev -- was a deliberate attempt to set the election for this year in order to leave the opposition with little time to prepare a challenger.
"I think the election will be held this year, there is no doubt about it," Tuyakbai said. "I believe they are likely to be set for the first Sunday of this December. Now they [authorities] are considering different alternatives for how to organize it, including the possibility of organizing it with the help of the parliament."
Before today's announcement, the constitutional debate had left many Kazakhs, such as these polled in Astana, confused about when the vote would ultimately be held.
First woman: "In December 2006."
Second Woman: "I don't know."
Man: "In fact, a seven-year term expires in December . He was elected in January, right? So, I think elections must be held in December 2005."
Under current Kazakh legislation, the Constitutional Council decision must be confirmed by both houses of parliament. Observers say this is largely a formality, as both the Mazhilis and the Senate are seen as almost exclusively pro-Nazarbaev.
The Senate today was in the process of being selected by regional and local officials and Nazarbaev himself, with no popular voting involved. Otan candidates were expected to make up a majority of the seats, and no opposition candidates were in the running.
Experts say Nazarbaev is likely to win the early December poll, as his popularity remains high. The Kazakh parliament abolished presidential term limits in October 1998. If he wins, this would be Nazarbaev's third term in office.
Critics say the last-minute decision to set an early date works to the distinct disadvantage of the political opposition, which is seen as weak, fragmented, and poorly organized. Dosym Satpaev, a political analyst with the Risk Assessment Group analytical center in Almaty, told RFE/RL: "The delay of the decision on a final election date was nothing but a deliberate political move by the government. It was aimed at misleading the opposition, which was unable to distribute its human, financial, and information resources [for the election campaign] before the final legal decision was made."
Observers say Kazakh authorities have led a widescale campaign aimed at weakening the political opposition.
Earlier this month, a criminal case was launched against Bulat Abilov, a co-chairman of the opposition party Naghyz Ak Zhol (The True Bright Path). Abilov, who is also a wealthy businessmen, was accused of fraud and tax evasion.
For a Just Kazakhstan leader Tuyakbai is considered the strongest opposition presidential candidate. He sent an open letter to Nazarbaev on 17 August confirming his intention to run for president. He said he was not deterred by a warning from the Kazakh Prosecutor-General's Office about having violated election laws by campaigning before the date was set.
The international community is likely to watch the upcoming elections closely, following the "color revolutions" that swept the ruling elite from power in Georgia, Ukraine, and Kyrgyzstan after elections there were deemed to be rigged.
Earlier this month, U.S. President George W. Bush wrote to Nazarbaev and urged him to follow fair election procedures whenever the presidential vote was held.
In a meeting in Brussels on 19 July, European Union officials said they will also be watching the presidential elections as an important test of Kazakhstan's commitment to democratic reforms.
(RFE/RL's Kazakh Service contributed to this report.)