Jenkins told the Evening Post: "There are one or two players within the squad who, for whatever reason, are looking to keep their options open.
"They are not accepting the terms that are on offer at this stage and, as a football club, we just have to accept that they are within their rights to do that."
Meanwhile, manager Paulo Sousa is taking a close look at French trialist Gregory Lorenzi.
Sousa is in the hunt for central defensive cover and has handed Lorenzi a three-day trial this week.
The 25-year-old, who started his career at Nantes, is currently with French Ligue 2 side Stade Brestois.