A few minutes later, Allen made a vow about his future.

“There’s still a lot of basketball left in my legs,” he said.

The Heat apparently were listening, apparently agree — and will soon officially welcome Allen to their club.

Allen told the Heat on Friday night that he intends to accept their contract offer and leave Boston after five seasons, even though the Celtics could have paid him about twice as much as the reigning NBA champions will be able to next season. Miami could only offer Allen the mini mid-level, worth about $3 million a year.

Heat owner Micky Arison tweeted the news just after 9:30 p.m. Friday, or about 2:30 a.m. Saturday in Europe, where Arison has been for several days.

“I was just woken up with great news,” Arison wrote. “Welcome to the family.” Arison ended the tweet by making mention of Allen’s jersey No. 20, but didn’t mention the NBA’s leading 3-point shooter by name. No matter — Allen’s agent, James Tanner, confirmed the plan to The Associated Press moments later.

A person briefed on details of the decision told the AP that Arison got the word from team president Pat Riley, who made Allen the team’s top free-agent priority — especially in recent days. Allen, who will be 37 this month, arrived in Miami on Thursday for a visit, went to dinner with Riley, coach Erik Spoelstra, team executive Alonzo Mourning and others Thursday night, then left Friday to presumably decide his future.

Hours later, the choice was known. Allen, who made a career-best 45 percent of his 3-point attempts this past season, cannot officially sign until Wednesday because of the league’s moratorium.

“HeatNation continues to grow,” Heat guard Dwyane Wade wrote on Twitter late Friday night. And Heat forward LeBron James, the league’s reigning MVP and Finals MVP, added “please welcome our newest teammate Ray Allen” with the hashtag of “Wow.”

It’s the latest free-agency coup for Riley.

During the blockbuster summer of 2010, the Heat convinced James, Wade and Chris Bosh all to take less money than they could have gotten elsewhere in that offseason, so there would be enough room left to add players like Udonis Haslem and Mike Miller (who both also took smaller contracts) and Mario Chalmers. Then last summer, Shane Battier accepted a deal that will pay him $3 million annually.

The approach clearly worked.

Next fall, the Heat will raise a championship banner, and Allen will be with them for the title defense.

Wade and James both were involved on some level in the recruitment of Allen. James took to Twitter and Facebook in recent days to let his millions of followers know how much he wanted to see Allen in a Heat uniform, and Wade tweeted on Wednesday that the next day — the one where Allen was visiting — would be a big one for the franchise.

In the end, it appeared that the biggest push — again — came from Riley, who said before free agency started that Miami had identified “five or six” clear targets to add to the roster. He never specifically said Allen, and given how James was letting the secret out on Twitter anyway, Riley didn’t have to say anything else.

New Orleans Hornets guard Jarrett Jack asked his followers in a tweet about an hour after the Allen story broke if he was “wrong for thinking ray allen is a traitor” for signing with Miami. Even NFL stars were reacting Friday night. Philadelphia Eagles quarterback Michael Vick used the following hashtags on Twitter to describe his reaction to Allen’s decision: “loaded,” ”finalpiece” and “notfair.”

There are probably more than a few people in Boston who would agree.

Miami is still hoping to add at least one more piece through free agency, and is expected to meet this weekend with Marcus Camby (who would most likely have to be acquired through a sign-and-trade if he was to wind up with the Heat) and Rashard Lewis.

Earlier this week, the Celtics reportedly agreed on a $15 million, three-year deal with shooting guard Jason Terry. But Boston also wanted to keep Allen, with general manager Danny Ainge quoted in recent days saying “we really want Ray to come back. Time will tell.”

Allen has made an NBA-record 2,718 3-pointers. He was mentioned in some trade possibilities this past season — a deal was nearly struck with Memphis — and Allen eventually lost his starting job to Avery Bradley. Allen needed surgery earlier this offseason to remove bone spurs from his right ankle, though he said when the Celtics were ousted from the playoffs by the Heat for the second straight year that his playing days were not over.

“It’s hard to say what can happen, what may happen,” Allen said after Game 7 of the East finals this year.

He said those words in Miami. Not even a month later, Allen — who helped the Celtics win the 2008 NBA title — decided to join the Heat.

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