Hillary ClintonHillary Rodham ClintonThe Trail 2016: The establishment comes around Sanders asks for extension on financial disclosure forms Poll: 1 in 4 voters would sit out Trump-Clinton showdown MORE will speak at the McCain Institute's annual Sedona Forum on Saturday with Sen. John McCainJohn McCainMcCain fundraiser faces felony drug charges in Arizona GOP senator blocks Obama Army nominee over Guantanamo Bill would target retaliation against military sexual assault victims MORE (R-Ariz.), the institute announced Thursday.
In a statement, McCain said he is "very pleased" his "friend" Clinton could join this year's forum.
Both served in the Senate together when Clinton represented New York from 2001 until 2009. She lost the 2008 Democratic primary to President Obama, and he appointed her to be his first secretary of State.
Clinton is now being closely watched to see whether she moves the needle on a potential 2016 presidential bid.
This year's forum focuses on "Crisis in the Middle East: Values, Strategy and Options." Sessions will also cover issues regarding Ukraine and Russia, and combating human trafficking.
Other lawmakers attending the event include Sens. Kelly Ayotte (R-N.H.), Bob Corker (R-Tenn.), Heidi Heitkamp (D-N.D.), Angus King (I-Maine), Amy Klobuchar (D-Minn.) and Sheldon Whitehouse (D-R.I.).
U.S. Deputy Secretary of State Ambassador William Burns, who's retiring later this year, will also attend.
The institute said business leaders, philanthropists, activists and experts on solutions to "real-world problems" will participate in the forum as well.
Last year's Sedona Forum featured remarks from Vice President Biden and six heads of state, among others.