WASHINGTON (AP) — Sen. John Kerry, the next secretary of state?

Republican Sen. John McCain had some fun Monday at the expense of his friend and Democratic colleague. Responding to a Kerry introduction at a news conference on a disabilities treaty, McCain said, ‘‘thank you very much, Mr. Secretary.’’

It was a clear reference to the recent talk that Kerry is a top candidate to replace Secretary of State Hillary Rodham Clinton. It was also a nod to McCain’s opposition to the current front-runner, U.N. Ambassador Susan Rice.

Kerry gave it back with his own quip, one that pained McCain.