Lionel Messi said today he was delighted to have signed for French club Paris St Germain and that he was ready to help the team clinch their first ever Champions League title.

"That's why I am here. It's an ambitious club," Messi told a news conference. "You can see they're ready to fight for everything.

"My dream is to win another Champions League, and I think this is the ideal place to be to do that."

The Argentinean conceded he did not know when he would be able to make his debut given he has not played since winning the Copa America with his country last month.

"I'm coming back from holiday, I've been a month off the pitch," he said.

"I need a bit of a pre-season and get myself going. Hopefully debuting can be soon but I can't give you a date. It's up to the coaches."

Messi on Sunday wept as he told Barcelona fans he was leaving his childhood club, and admitted that while he is sad, he is looking forward to the new challenge.

"I'll always be thankful to Barca and their fans. I went there as a boy, and we had some good and bad times," he said.

"The Barca fans knew I'd join a good club, fighting for the Champions League, because they know me, I like to win, I'm a winner and I want to carry on doing that.

"I don't doubt that PSG's objectives is to win and grow. It would be nice on the one hand to face them in the Champions League, especially with fans, but on the other strange to go back to my home in another team's shirt - but that's football."

Meanwhile, the club's president  claimed the signing  was in line with European football's financial fair play rules.

"We follow the financial fair play rules," Nasser al-Khelaifi said alongside Messi.

The owners of PSG, the deep-pocketed Qatar Sports Investment, have spent lavishly on its star-studded line-up in recent years.

Al-Khelaifi said people would be "shocked" by the financial revenues Messi would bring the club, though he quipped: "I hope Leo will not ask for more salary." 

Al-Khelaifi believes the arrival of Messi will be decisive in keeping 22-year-old France striker Kylian Mbappe, whose contract expires next year.

"He wanted a competitive team and I think we have the most competitive in the world so there is no excuse for him now, he can't do anything else but stay," added the president, who defended the club's spending.

"What you as a media need to focus is not only the negative side but the positive side he will bring to the club.

"We checked with our financial people and knew that we could sign him.

"Through it all we look at Financial Fair Play and always we will fulfil Financial Fair Play regulations."