Michael Buble's wife Luisana Lopilato insists the "worst is over" in terms of their son's cancer battle.

Michael Buble and Luisana Lopilato

Michael Buble and Luisana Lopilato

The couple's three-year-old son Noah was diagnosed with the disease in November 2016 and while the 30-year-old actress still has sleepless nights due to the little one's condition, the pair - who also have 17-month-old son Elias - are trying to "be strong" for their boy.

She said: "There are things that happen in life that make you realise that the most important things that you think are important, really aren't.

"The most important thing is to have faith and to be strong. There are nights that I still don't sleep and I pray to God because it's still a long process and the worst is over. Thank God.

"When I was down, my mom told me, 'Be strong, your son will be fine.' "

Noah was initially diagnosed with mumps and swollen glands before further test results discovered he had cancer, and Luisana, who was in Buenos Aires at the time, was so devastated she couldn't tell her husband over the phone so jumped on a plane to Los Angeles.

In a video with Argentinian TV host Susana Giménez on the presenter's YouTube channel, Luisana added: "They ran lots of tests, blood analysis, everything. When they did an ultrasound, they said they found something in his stomach. [Doctors] told us they weren't sure what it was, but it was a tumour.

"I couldn't speak to him [Michael] by phone. So I got on a flight. Without speaking to Mike I took the flight."

The 'Haven't Met You Yet' hitmaker was in England at the time doing an interview, but the couple have a rule that they will meet in the middle in Los Angeles if anything bad happens to their family.

The couple cancelled all of their scheduled appointments to care for their son.

Last month, Michael made his first public appearance since Noah's cancer diagnosis at the 2017 Governor General's Performing Arts Awards in Ottawa, Canada, and he gave a heartfelt speech about the youngster.

He said: "I've learned that people will forget what you said, people will forget what you did, but people will never forget how you made them.

"I think these words are a perfect description of how I've always felt as an artist and as a person, and the reason why we're here today. My entire life has been inspired by how my family has made me feel - my wife, my children, my parents, my sisters ....

"There are no words to describe how I feel about you. Sometimes 'I love you' just isn't enough because what I feel is so much more."