New York City FC star Andrea Pirlo says Major League Soccer must change its rules on transfers and salaries if it is to compete with the likes of the Chinese Super League.

Pirlo, 37, said he has seen the game grow in the United States since he arrived from Juventus in 2015 but feels there is a risk MLS will start to lose popularity if it does not evolve.

The Italian says the salary cap must be scrapped and free movement of players needs to be introduced if the league wants to compete for top stars.

"I've seen improvements and from what I have seen in friendly games and the first two rounds of the regular season, the quality has risen a lot," Pirlo told La Gazzetta dello Sport. "Certainly I would get rid of the restrictions on the transfer market, though.

"Enough with the three exceptions to the salary cap, which is too little to convince other stars to come here. They need to develop a liberal system where you can buy and sell players without restrictions.

"Now there is even the competition from China. Especially if you want to compete with other leagues, at home and abroad, you have got to get rid of any restrictions."

Andrea Pirlo, left, and David Villa, right, are among MLS' top stars. EDUARDO MUNOZ ALVAREZ/AFP/Getty Images

MLS clubs are allowed three "Designated Players" whose annual salary can exceed $480,625.

In 2015, the league amended its rules to make it possible for clubs to add more "high-earning" players, but the rules on salary budgets for non-Designated Players -- $3,845,000 per team in 2017 -- remain restrictive.

MLS Confidential, ESPN FC's annual anonymous player poll, saw 79 percent of those responding say they were not happy with the league's salary structure.

Meanwhile, Pirlo said he has yet to decide whether he prolong his career when his contract expires at the end of this year.

"I've not decided yet -- I'm just focused on my work and trying to do this without thinking of the future," Pirlo said. "When I do retire, I am going to go back to Italy."

He said he does not regret leaving Juventus so soon after playing in their Champions League final defeat to Barcelona.

"I do miss those games a lot -- they are the most beautiful games to be involved in no matter what age you are, but in July 2015 I made a choice and I don't regret it," he said. "As the years go by, you have to realise when it is the right time to do something different.

"It's best to make that decision to leave yourself, when you are still feeling good, rather than have somebody else point it out for you. I'm now into my third season here and we want to push on. For example, we want to win the East Conference and try to push ourselves as far as we can go in the playoffs."