Bruce Willis will step away from his acting career after being diagnosed with aphasia, a condition that impedes a person's ability to speak and write.

The actor's family, including his wife Emma Heming-Willis and ex-wife Demi Moore, announced his condition on Instagram on Wednesday.

Aphasia is "impacting his cognitive abilities", the statement said.

Willis, 67, is best known for playing John McClane in the Die Hard films, which made him a star.

"With much consideration Bruce is stepping away from the career that has meant so much to him," his family wrote in a joint statement. "This is a really challenging time for our family and we are so appreciative of your continued love, compassion and support."

Willis has five daughters, three with Ms Moore and two with Ms Heming-Willis.

What is aphasia?
*It's when a person has difficulty with their language or speech
*Usually caused by damage to the left side of the brain, like a stroke
*Hampers reading, listening, speaking, typing or writing
*Speaking problems are most common and can involve putting words together incorrectly

His acting career began in the early 1980s but he did not become a household name until later in that decade - first after starring opposite Cybill Shepherd in the ABC TV series Moonlighting and then in his 1988 performance as John McClane in the first Die Hard film.

Since then, his films including The Sixth Sense, Armageddon and Pulp Fiction have grossed more than $5bn worldwide, according to Variety. He's been nominated for five Golden Globes, winning one for Moonlighting, and three Emmys, winning two.

Several actors and other stars offered their condolences to Willis and his family following the news.

"Grace and guts! Love to you all!" actress Jamie Lee Curtis wrote in response to Demi Moore's post.

"Sending lots of love and healing to you all!" wrote journalist Katie Couric.