The president of the European Parliament, Italian social democrat David Sassoli, has been seriously ill in hospital for more than two weeks, his spokesman said Monday.

Sassoli will be unable to chair next week's session of the parliament in Strasbourg, at which his successor as speaker will be chosen just ahead of the end of his two-and-a-half year mandate.

His first vice president, Maltese MEP Roberta Metsola, is in the running to replace him.

"This hospitalisation was necessary because of a serious complication due to a dysfunction of the immune system," Sassoli's spokesman Roberto Cuillo said.

"As a result, all official activities of the President of the European Parliament have been cancelled."

The 65-year-old former television news reader has been in hospital in Italy since December 26. He was previously admitted with pneumonia for several weeks last September.

The European Parliament sits for a five-year term between elections, but the president of the body serves for half that time and Sassoli had already indicated that he would not seek re-election.

On Tuesday next week, MEPs are expected to hold the first round of voting for his successor.

Metsola was among those to offer their support, tweeting her solidarity to Sassoli and his family "during this difficult time".