“I feel really awful,” said the actor Saturday, who had charity work commitments. On Sunday, Shatner took to Twitter to defend his absence at Leonard Nimoy’s funeral.

Leonard Nimoy and William Shatner, pictured on Aug. 19, 2006.

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"I loved him like a brother. We will all miss his humor, his talent, and his capacity to love," Shatner said on Twitter.

Nimoy, famous for playing the Vulcan Mr. Spock, died Friday from end-stage chronic obstructive pulmonary disease at the age of 83.

"I am so humbled by the worldwide outpouring of love that has been displayed; words cannot express my feelings," Shatner wrote.

William Shatner, DeForest Kelley, and Leonard Nimoy in Star Trek.

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