Venezuelan President Hugo Chavez is undergoing cancer surgery in Cuba, Ecuador's president has said.
"Commander Hugo Chavez is being operated on at this moment. It's a very delicate operation," Rafael Correa said at an event in the city of Tulcan.
"At this time he's passing through one of the hardest moments of his life. Our heart and our solidarity go out to a historic president."
Mr Correa, a close ally of the Venezuelan leader, travelled to Cuba on Monday and met with Mr Chavez.
Mr Chavez announced on Saturday that he needed to undergo a fourth cancer-related surgery after tests showed that "some malignant cells" had reappeared in the same area where tumours were previously removed.
Mr Chavez also said for the first time that if his illness cuts short his presidency, vice president Nicolas Maduro should take his place and should be elected president to lead his leftist movement.
It is his third operation to remove cancerous tissue from his pelvic area in about a year and a half. An initial surgery for a pelvic abscess in June 2011 helped reveal he had cancer.
Mr Chavez has also undergone chemotherapy and radiation treatments.