PUR - Beltran in late talks with players before squad announcement
Napier, the Most Outstanding Player of this year's NCAA Tournament Final Four after leading the University of Connecticut to the title, is preparing for his rookie season in the NBA with the Miami Heat.
The 22-year-old is playing with the Heat's Summer League team.
Harkless, 21, spent his second campaign with the Magic in 2013-14.
Puerto Rico have already drawn up preliminary squad lists for the Centrobasket and FIBA Basketball World Cup but are not expected to make them public until next week.
"I am one who would rather not comment until I have everything ironed out," said basketball federation president Carlos Beltran.
"We are trying to get the commitment of Shabazz Napier and Maurice Harkless.
"Both still have not been made it clear as to whether or not they are playing, but we keep doing the steps."
The Centrobasket will be staged 1-7 August in Nayarit, Mexico, and the World Cup tips off in Spain on 30 August.
Carlos Morales, meanwhile, is to be in charge of the Boricuas' practices that get underway on 11 July with national team boss Paco Olmos still coaching Cangrejeros Santurce in the Puerto Rican league.
"Once he finishes with Cangrejeros, Paco will be fully integrated," said Beltran.
"But his assistants will be those who run the show while he finishes so he can concentrate on his work in Santurce."
Puerto Rico are looking to improve on their past two showings at the FIBA World Championship.