The election is being closely watched at a time of high tensions with North Korea.
“The case is very grave as the suspect has demonstrated acts of abuse of power," the prosecutors' office says.
Paul Ryan said he hopes to be finished by the April recess.
Park Geun-hye is the country's first democratically elected leader to be forced from office.
The indictments are the latest twist in a corruption scandal that has gripped the country for months.
And he called NATO "obsolete."
The presidential nomination of former First Lady and Secretary of State Hillary Clinton has received extraordinary attention across the globe. That heightened awareness has brought into focus how well other women - particularly in Asia - have done in terms of rising to political leadership.
MANILA, Philippines -- "The people never give up their liberties but under some delusion," Edmund Burke, the great 18th century conservative thinker, once warned. Today, a specter is hunting the democratic world -- the specter of autocratic nostalgia.
Four decades ago South Korea's President Park Chung-hee, father of the current president, launched a quest for nuclear weapons. Washington, the South's military protector, applied substantial pressure to kill the program. Today it looks like Park might have been right.
Reunification, for Koreans, has a mythic quality. Most Koreans dream of reunification, of a time in the future when the North and the South will join together to recreate the Korean whole that existed before division and Japanese colonialism. It's a lovely idea, but no one has a very good idea of how to achieve it.