William Shatner has been forced to miss his Star Trek co-star Leonard Nimoy's funeral due to prior commitments.

A burial service for the Jewish actor will take place in Los Angeles, but Shatner will not be able to mourn the death of his friend in person as he had already agreed to attend a charity ball in Florida and will not have enough time to fly across the US to make the memorial.

He took to Twitter to express his disappointment, writing, "I feel really awful. Here I am doing charity work and one of my dearest friends is being buried."

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Nimoy died at his Los Angeles home on Friday after losing his battle with chronic obstructive pulmonary disease.

Shatner, who played Captain Kirk opposite Nimoy's Mr. Spock on TV and in movies for two decades, was among the first to pay tribute to his old pal following the news of his passing.

In a statement, Shatner revealed he loved the late actor, photographer and director "like a brother", adding, "We will all miss his humour, his talent, and his capacity to love."

Today on Twitter Shatner celebrated his late friends life by answering fan questions about Nimoy: