Kigali - Rwanda will vote on December 18 on a referendum to allow President Paul Kagame to run for re-election when his current seven-year term ends, a move that's opposed by the US.The government set the polling date in a statement late on Tuesday.Kagame, 58, is ineligible to run in 2017 because the Rwandan constitution limits a president to two terms. But if Rwandans vote to change the term restriction, Kagame would be able to run for an additional seven-year term and then two-five terms, he could possibly stay in power until 2034.Kagame became president in 2000 after being Rwanda's de facto leader since the end of the country's genocide in 1994. He is credited with stabilizing and promoting economic growth in the country after the mass killings, but critics say he is an authoritarian ruler who does not tolerate opposition.The move to change the constitution was prompted by a petition which more than 3.7 million people signed calling for a change in the constitution. It was endorsed by the Senate and the lower house of Parliament last month and later by the country's Supreme Court.Rwanda's political opposition criticizes the move as undemocratic. Opposition leader Frank Habineza said the petition was "engineered by the ruling party and not ordinary Rwandans."The Obama administration has advised Kagame, one of America's closest allies in Africa, not to consider a third term as president."In the Central African region, we're very concerned about growing political instability," US ambassador to the UN Samantha Power said in New York on Tuesday. "One of the disturbing trends that we've seen is a desire for leaders to extend their tenure in office in a variety of ways. ... There is an unfortunately sizeable list of countries that are considering changing their constitutions or changing the rules of the game in order to retain power."If Rwanda's term limits are changed and Kagame runs again, he will join a growing list of leaders in East and Central Africa whose governments have extended their rule by changing presidential term limits.In 2005, Ugandan lawmakers changed that country's constitution, allowing President Yoweri Museveni to seek re-election in 2006 and 2011. He is expected to run again in 2016.Neighbouring Burundi has political unrest that started earlier this year when President Pierre Nkurunziza changed the constitution to allow him to run and win a third term in July.There have also been protests in Congo over efforts by President Joseph Kabila, who has been in power for 15 years, to prolong his time in office.