Pastrnak, 21, is coming off a breakout season; his production increased from 26 points (15 goals, 11 assists) in 51 games in 2015-16 to 70 points (34 goals, 36 assists) in 75 games last season. Pastrnak and the Bruins would like to have a contract before training camp opens in September.
Pastrnak told NHL.com his focus this summer has been on his offseason training program rather than contract negotiations.
"I'm just waiting, leaving it all to my agent [J.P. Barry] to communicate with them," Pastrnak said during the European Player Media Tour in Stockholm last Thursday. "I'm just focusing on getting ready for next season.
"I'm focusing on getting better and I'm trying not to think about that stuff. I just let it go and something will happen."
Sweeney said he met with Pastrnak's representatives during development camp last month and was hopeful of a resolution, but there was no time frame given.
"We will continue to negotiate; we still have lots of time," Barry told the newspaper in an email. "David prefers to sign a longer-term deal with the Bruins.
"The negotiations between myself and Don have been very open and both sides understand each other's positions. Hopefully we can agree on an overall structure that is amenable to both sides in the next month."