ALMATY, Kazakhstan (AP) — Kazakhstan's aging leader will seek to extend his rule to 2017 in the energy-rich nation's next election and may even seek to stay in power until after 2020, a presidential adviser said Thursday, dampening speculation about potential successors.

President Nursultan Nazarbayev revealed plans to seek an extension to his two-decade-long rule during a conversation earlier this month, senior adviser Yermukhamet Yertysbayev told The Associated Press in a telephone interview.

Yertysbayev said the president was even prepared to stand for a further five-year term in 2017.

Speculation about potential successors to Nazarbayev has flourished in recent years in the Central Asian country, but signs that the iron-fisted leader plans to extend his rule in the 2012 election is likely to put those predictions to rest.

Yertysbayev also dismissed rumors about plans by Nazarbayev to dispense with the need for elections and rule indefinitely.

"According to the constitution, there should be an election, and that is what is going to happen," Yertysbayev said.

Nazarbayev, an omnipresent figure in Kazakh political life, has no real challengers to his authority and re-election is all but guaranteed.

Although critics will see the announcement as an indication of the president's determination to hang onto power, Yertysbayev said the longevity of Nazarbayev's rule will ensure the prosperous development of the oil-rich country's economy.

"During his rule, he wants to complete an entire industrial development program" and develop an innovative economy, Yertysbayev said.

Nazarbayev has ruled Kazakhstan unchallenged since the late 1980s when it was still part of the Soviet Union and repeatedly been elected to high office by landslide victories.

Some have expressed misgivings that the 70-year-old leader may not be in sufficiently good health to run the country into his eighties, but Yertysbayev said those concerns were unfounded. "He feels fantastic, both physically and mentally," he said.

Nazarbayev signed off on changes to the constitution in 2007 allowing him to run for office an unlimited number of times. However, under those rules, succeeding presidents will only be permitted to stand for two five-year terms.

In a move that drew vocal criticism from the pro-democracy camp, Nazarbayev declined earlier this year to reject a law overwhelmingly approved by both houses of parliament to appoint him "Elbashi," which is Kazakh for leader of the nation.

The title effectively made Nazarbayev leader for life, giving him the right to approve important national and foreign policies after he retires, as well as granting him lifetime immunity from prosecution for acts committed during his rule.

Other measures passed by lawmakers made defacing images of Nazarbayev an offense and provided property owned by him and his family protection from confiscation.

The prospect of Nazarbayev cementing his hold over the country will reawaken concerns over Kazakhstan's commitment to adopting democratic reforms.

Kazakhstan has come under sustained criticism this year, as it chairs the Organization for Security and Cooperation in Europe — a trans-Atlantic group that includes democracy-promotion as one of its main goals.

Nazarbayev's Nur Otan party won all the seats in a parliamentary election in 2007 that was deemed flawed by international observers, prompting new accusations of authoritarian rule.

Western governments had hoped Kazakh chairmanship of the OSCE would prompt authorities to undertake major political reforms, but critics say little has been done to raise democratic standards.

Nazarbayev has routinely dismissed criticism of poor progress on democratic development, arguing that economic and political stability are of primary importance.