CNN

Former President Bush made a surprise appearance at a McCain event Monday in South Carolina.

(CNN) - There was a surprise guest, albeit by videotape, at the final stop of John McCain's "No Surrender" tour in South Carolina on Monday night.

Former President George H.W. Bush spoke to the crowd at The Citadel in Charleston, thanking McCain for "standing tall" in his support of the war in Iraq.

"The bottom line is we must persevere, we must not surrender. We must not quit and run away," Bush said. "God bless our troops and everyone involved in the 'No Surrender' rally there in Charleston."

The Bush camp was quick to point out the appearance was not an endorsement of McCain, and was a one-time-only event.

Bush spokeswoman Jean Becker told CNN Bush was asked to make the tape by his longtime close friend Robert Mosbacher, the former Commerce Secretary and party fund-raiser who backs McCain and is serving as his general chairman.

The timing of McCain trip, following Gen. David Petreaus' report to Congress and the president's speech Thursday on war policy, is what led Bush to agree to the taping, she said.

He is grateful for McCain's rallying of support for President Bush's Iraq policy, she said. The former president "definitely supported what he was saying and his support for the troops."

Bush considers McCain "a good friend, but he also considers Rudy Giuliani, Mitt Romney and Fred Thompson good friends," Becker said.

She said Bush spoke without a script, ad-libbing the brief remarks.

– CNN Political Desk Managing Editor Steve Brusk