The Flyers picked up the rights to Streit last week from the New York Islanders in exchange for a fourth-round pick in the 2014 NHL Draft.
Streit was scheduled to become an unrestricted free agent on July 5.
The 35-year-old had six goals and 27 points in 45 games with the Islanders in the 2012-13 season, and added two goals and five points in six playoff games.
Streit spent the past four seasons with the Islanders, serving as their captain since 2011. He missed an entire campaign in 2010-11 due to a shoulder injury.
"We continue to have talks with Mark's agent," Flyers general manager Paul Holmgren said in a statement. "Although there is nothing to report, we remain confident that we will get something done."
The Swiss blue-liner was a ninth-round pick by the Canadiens in 2004, and played three seasons in Montreal before signing with the Islanders in 2008. He led the Isles in scoring that year with 56 points and was selected to appear in his first NHL All-Star Game in 2009.