Messi joined Paris Saint-Germain in August after Barca decided not to renew the Argentinian’s contract due to La Liga’s strict salary limits.
"There came a time when both parties saw that it would not be possible. There was disappointment on both sides," Laporta told Catalan radio station RAC1.
"He wanted to stay but they also had a lot of pressure because of the offer they had. They knew if he didn’t stay, he would go to PSG."
Laporta continued: "I hoped Messi would do a u-turn and he would say he would play for free.
"I would have liked that and I would have been all for it. It is my understanding La Liga would have accepted it. But we cannot ask a player of Messi's stature to do this."
Laporta reiterated the club’s atrocious financial situation meant they were unable to keep Messi on the same terms.
Barca recorded losses of 481 million euros ($556 million) last season, with a gross debt of 1.35 billion euros.
"We had the conclusions of the audit (on Wednesday) and the investment in Leo would have put us at risk," said Laporta, who also suggested Barcelona could yet sign up to a deal with investment fund CVC Capital Partners.
La Liga told Barca in August they could keep Messi if they agreed to the deal, which involved the league selling 10 percent of the commercial business, including television rights, for the next 50 years, in exchange for 2.7 billion euros.
Barcelona, Real Madrid and Athletic Bilbao rejected the offer.
"We do not need more debt," said Laporta. "I understand La Liga clubs are suffering. We have not ruled ourselves out of this operation but they have to change it. They are trying to reformulate the deal."
Laporta also confirmed his support for Barcelona coach Ronald Koeman, whose future has been uncertain in recent weeks.
"I think he deserves a margin of confidence," said Laporta. "I asked him if he trusted the team and he said, 'Of course I trust them. I need to get the injured players back'. He wants to continue at all costs and show this team is competitive."
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