"NCIS" will press its luck to keep the title of most-watched drama series for another two years. CBS announced on Monday that it has renewed the top-rated show for two more seasons.

Seasons 14 and 15 will keep "NCIS" on the air through 2018. Series star Mark Harmon also inked a two-year deal with CBS TV Studios and will continue to lead the team as Special Agent Leroy Jethro Gibbs alongside his co-stars Pauley Perrette, Sean Murray, Emily Wickersham, David McCallum, Rocky Carroll and Brian Dietzen.

The CBS procedural will lose one of its four original stars, Michael Weatherly, at the end of this season. He has starred on the show since its premiere in 2003 with Harmon, Perrette and McCallum.

"It's extraordinary that in its 13th season and with over 300 episodes to its credit, 'NCIS' continues to excel at such a high level on a global scale," Glenn Geller, President, CBS Entertainment said in a statement. "It is testimony to an amazing cast, led on and off the screen by the exceptional Mark Harmon, for skillfully bringing this universally appealing team of heroes to life; and to Gary Glasberg and his writers for crafting compelling stories that feature NCIS's signature blend of mystery, quirk, drama and comedy every single week."

"NCIS" will celebrate its 300th episode on March 15. The episode will feature special guest star Taye Diggs as a wounded warrior who is being treated for PTSS at Walter Reed Medical Center six months after his group of Special Ops snipers was ambushed in Iraq.

Next fall, "NCIS" will introduce two new characters, a male and female agent. The show is looking for a big name actress to play the role of Tess, an FBI Special Agent who shares a few characteristics with Harmon's Gibbs.

"NCIS" airs on Tuesdays at 8 p.m. on CBS.