Kevin Costner Speaks at Whitney Houston Memorial After Dionne Warwick’s Call (Exclusive)

In the days following Whitney Houston’s death, Kevin Costner was invited to participate in numerous public tributes.

Although he and Houston, who died aged 48 on February 11, 2012, developed a close bond during the filming of their hit 1992 film. The bodyguardCostner initially chose to mourn his friend in private.

Until Dionne Warwick called.

“Whitney was definitely worth talking about, but it’s not my first instinct to go over there, to rush to the mic,” the Oscar winner, 69, told PEOPLE in the This week’s cover story. “But I got a call from Dionne Warwick and I could tell in her voice that she was broken. I told her yes even though I had been saying no all week.”

“I heard in her voice how tired she was, how many decisions she probably had to make, who would speak, who wouldn’t speak,” Costner continues. “She said, ‘Kevin, can I ask you?’ and I (just) said, “Yes.”

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But he immediately hesitated.

“I ask myself, ‘Why am I I Speaking? I was just his imaginary bodyguard,” he says, admitting that he made “a promise to protect” Houston during filming.

“I didn’t read the tea leaves correctly, how much it meant to other people,” he explains.

Costner remembers being deeply moved by his experience at the memorial, held at New Hope Baptist Church in Newark, New Jersey.

“I remember being in the pews and I had never been in a more electric church,” he says. “Two bands were playing…I thought this place was on fire.”

When someone informed Costner that he might want to keep his speech short since “CNN is covering this,” he bristled.

“I said, ‘I’m sorry, I didn’t realize CNN was there, but they can do a commercial break,'” the actor told PEOPLE. “‘I’m going to say what I want to say. I’ve come a long way to talk about this little girl.’ ”

Before taking the stage to deliver what would be a heartfelt 17-minute eulogy, Costner said the nerves had returned. “I remember looking back and seeing Diane Sawyer and Oprah Winfrey…I think they were sitting together, and I was like, ‘Can you do my speech?’ “, he remembers.

“I really wanted them to do it. I didn’t want to go up, but I did it,” Costner adds.

For more on Kevin Costner, check out this week’s issue of PEOPLEon newsstands Friday.