Laporta, who was previously Barca president between 2003 and 2010, was voted in by club members last weekend but had to secure a €125 million bank guarantee before being inaugurated.
Now in office, one of his first tasks is convincing Messi, who turns 34 in June, to extend his contract, which expires the same month, beyond the end of the season.
Messi, who wanted to leave last summer, voted in last Sunday's election and was seated in front of Laporta as he made his speech at Camp Nou on Wednesday in front of around 300 invitees.
"I will try to convince Leo to stay at the club," Laporta said, turning his attention towards Messi near the end of a 30-minute speech as the rest of the attendees clapped.
"Sorry Leo, but I will do my best, he knows it. We're going to try and convince him to stay because he's the best ever and, forgive me for this Leo, but I love you and Barca loves you, too.
"If this stadium was full, I'm sure you couldn't leave -- another issue caused by this damned pandemic! Whatever his decision, it will be fine, but we're going to try [and keep him]."
Throughout the electoral campaign, Laporta stressed that he was the most likely of the candidates to persuade Messi to stay at Barcelona.
Laporta was the president at the club when Messi broke into the first team and signed his first professional deals and the two have maintained a good relationship since.
Paris Saint-Germain and Manchester City continue to monitor Messi's situation. The Argentine told the previous board, presided over by Josep Maria Bartomeu who Messi has branded a liar, that he wanted to leave last August but he wasn't allowed.
Since then, and following Bartomeu's resignation in October, Messi said he hasn't decided what he will do beyond the summer and will make a decision at the end of the season, giving Laporta time to make him an offer.
Koeman's future was also a source of speculation during the election campaign, with reports claiming RB Leipzig's Julian Nagelsmann and Arsenal's Mikel Arteta were options to replace him if Laporta was elected.
However, with Barca cutting the gap on leaders Atletico Madrid to four points and progressing to the final of the Copa del Rey, the Dutch coach has been backed by the incoming executive board.
"Ronald, you have the board's confidence," Laporta added. "The team has improved and we have to get back to winning things.
"If we fix things financially, we will be competitive once again in the Champions League. We can win La Liga and the Copa del Rey this season."