The 19-year-old has established himself as a regular in Guardiola's line-up since Project Restart and could play a significant role in the end-of-season Champions League tournament in August.
Garcia has two years remaining on his current contract and City’s director of football Txiki Begiristain was set to sit down with the player's representatives before the Covid-19 outbreak.
He joined City from Barca's La Masia academy for just over €1.7million (£1.5m) three years ago and the Spanish giants are keen to take him back.
"If they want him they must call Txiki," Guardiola said after the 5-0 victory over Newcastle on Wednesday night.
"We are going to try to convince him to stay here for many, many, many years.
"I’m confident he will stay but at the end of the day it’s his decision. He knows we want him.
"But it is similar to Leroy [Sane]. We wanted him but he didn’t want to stay and we cannot do anything else.
"He knows, his agent knows, and his family knows that we want him. He’s young and if Barcelona want him, they have to call Txiki."
Barca’s academy director Patrick Kluivert has previously suggested that the door is open for a potential return for a player who has been likened to Gerard Pique - a club legend that spent time in Manchester with City's rivals United before a triumphant return home.
But Guardiola is a huge admirer of the teenager, praising his maturity and intelligence.
The Spain U21 international started the first game after Project Restart - a 3-0 win over Arsenal - but suffered a concussion after a horrible collision with his own goalkeeper, Ederson, late in the game.
City are expected to be in the market for a new central defender at the end of the season, with Napoli's Kalidou Koulibaly among a number of targets being considered, but Garcia is seen as the long-term future for the club.