The United States must "at a minimum" prevent Taliban insurgents from returning to power in Afghanistan, Defense Secretary Robert Gates said in an interview on Tuesday. While President Barack Obama's administration was still reviewing US strategy in Afghanistan, Gates said that the US effort would have to ensure the Taliban would not rule the country again after being ousted in 2001. "I would say that at a minimum, the mission is to prevent the Taliban from retaking power against a democratically elected government in Afghanistan, thus turning Afghanistan, potentially again, into a haven for Al-Qaeda and other extremists," Gates told media. The defense chief was asked if the administration's goal was to gain a strong enough position to pursue negotiations with elements of the insurgents, but he did not speak directly to possible talks with the Taliban. "The specific mission is clearly one of the subjects under review by the administration right now. And I think we have to wait until that's done to have real clarity on that," he said. Obama and Vice President Joe Biden said this week that possible negotiations with elements of the insurgents should be considered; with Biden saying on Tuesday it was an option "worth exploring." Taliban insurgents, allied with Al-Qaeda, have rebounded in Afghanistan in the years since the US-led invasion toppled their regime in 2001.