From NBC's Mark Murray
NBC News confirms, per a source close to the senator, that Sen. Bill Frist will announce today that he will not run for president.

The Hotline reports that Frist will hold a press conference in his home state of Tennessee.

Frist, who is also a doctor, released a statement saying that after serving in the Senate for 12 years, he will return home to live a "private life" so that he can go back to his "professional roots as a healer."

"In the Bible, God tells us for everything there is a season, and for me, for now, this season of being an elected official has come to a close.  I do not intend to run for president in 2008," Frist writes.

He adds that he and his wife Karyn will take a "sabbatical from public life" and that in the interim he hopes to travel on "medical mission trips as a doctor around the world to serve those in poverty, in famine, and in civil war."