Michael Bublé's son begins "long and difficult" chemotherapy in cancer battle.

Last week, singer Michael Bublé revealed his three-year-old son Noah had been diagnosed with cancer, in an emotional Facebook post.

Now, Noah is set to undergo four months of chemotherapy in a battle against liver cancer.

Feliz día de la madre !! Happy Mother’s Day @luisanalopilato !! #myhero #bestmommy #bestfriend

A photo posted by Michael Bublé (@michaelbuble) on Oct 16, 2016 at 7:25am PDT

Argentian magazine Gente reports that Noah’s diagnosis was confirmed by LA doctors last week after they completed a liver biopsy.

The older sister of Bublé’s wife, actress Luisana Lopilato, told the publication that the family “had faith” that Noah would be able to overcome his illness.

The boys are chilling and feeding the ducks today. #daffy #donald #howard #AFLAC #leavenoduckbehind #quack

A photo posted by Michael Bublé (@michaelbuble) on Apr 8, 2015 at 1:55pm PDT

“Cancer is a horrible illness but we have faith in Noah being able to overcome this,” Daniela said.

“We know he will. The time to start a long and very difficult treatment has come but it’s got to be done. They say children are normally strong to put up with chemotherapy and my nephew is a warrior.”

Initial reports suggested that Noah was battling leukaemia, but Daniela revealed it was in fact liver cancer.

Gente also reports that Noah has a 90 per cent chance of beating the illness after undergoing chemotherapy, but may still need surgery to remove the tumour from his liver.

This is how the new tour begins. Off to rehearsals. We’re coming to a city near you !!! #getready #2017 #mbtour

A photo posted by Michael Bublé (@michaelbuble) on Sep 20, 2016 at 12:15pm PDT

“He has the innocence of children and that is good. He doesn’t understand too much what is happening,” Daniela said when asked how her nephew was coping.

Of their eldest son’s diagnosis, the singer said he and his wife were “devastated”.

I hate posting just anything , so Instead ,Im posting my everything. We’re on the best vacation ever. Lots of sunshine with my sunshine. #family #vacation #meandmyshadow

A photo posted by Michael Bublé (@michaelbuble) on Mar 5, 2016 at 3:43am PST

“We have always been very vocal about the importance of family and the love we have for our children. Luisana and I have put our careers on hold in order to devote all our time and attention to helping Noah get well,” Michael said in an emotional Facebook post.

“At this difficult time, we ask only for your prayers and respect for our privacy. We have a long journey in front of us and hope that with the support of family, friends and fans around the world, we will win this battle, God willing.”