U.S. Secretary of State John Kerry is headed to the Vatican to meet with a top papal diplomat — but isn't expecting to see Pope Francis himself.

Kerry stopped in Italy for a few hours Tuesday on his way to Kuwait for a conference later this week for humanitarian donors to Syria war victims. On Monday, Francis called for "renewed political will to end the conflict" in Syria.

Aides said Kerry is the first American Catholic secretary of state to visit since Edmund Muskie more than three decades ago.

He will meet with the Vatican's secretary of state, Archbishop Pietro Parolin.

It's generally uncommon for sitting popes to meet with foreign officials other than heads of state.