Democratic congressman John Lewis, an icon in the fight for civil rights, announced Sunday he has stage 4 pancreatic cancer.

"I have been in some kind of fight -- for freedom, equality, basic human rights -- for nearly my entire life. I have never faced a fight quite like the one I have now," Lewis said in a statement.

"So I've decided to do what I know to do and what I have always done: I am going to fight and jeep fighting...we still have many bridges to cross,"

Lewis said he is "clear-eyed" about the prognosis and that his doctors tell him he has a fighting chance.

House Speaker Nancy Pelosi tweeted that "generations of Americans" have Lewis in their thoughts and prayers, saying she knows he will be well.

The 79-year-old Lewis has represented the 5th Congressional District in Georgia since 1986 and has been a stalwart for liberal causes and human rights.

But Lewis is best known has a tireless fighter for civil rights -- he marched with Martin Luther King in the early 1960s, sat down at segregated lunch counters, and was the victim of police nightsticks and billy clubs, suffering from a fractured skull.

Lewis was an original Freedom Rider, traveling on busses across the south as part of the battle for integration.