The Venezuela-born Spain Under-21 forward has reportedly left Barca's pre-season tour of the United States in order to finalise the transfer, believed to be worth around 5million euros.
Jeffren looks set to undergo a medical in Portugal before puttiong pen to paper.
He told Portuguese newspaper A Bola: "It is almost all right.
"I go with high hopes. Sporting is a great club where I can play with the regularity that does not happen in Barcelona and also where I can fight for titles.
"I will chase these targets, not only in Portugal but I think in the Europa League we can also have good results."
Jeffren passed up the chance to move to Udinese last month as part of the deal which saw the European champions sign Chile winger Alexis Sanchez, with Barca instead affording the 23-year-old the chance to find a club that best suited him as he sought regular first-team football.
Barca coach Pep Guardiola told El Pais: "This was a mutual decision between the player and me. I told him if he wanted to play more, the best thing was for him to leave.
"For his age, he has to play. There could be three years without participating. The best thing for him is to leave, so that he can play more.
"His behaviour has been exemplary. I wish him all the luck in the world.
"He came through with us to the first team and has really helped us in everything. We appreciate everything he has done."
Source: Team Talk
Source: Team Talk