Henry's future beyond 2014 is up in the air with the 37-year-old's contract set to expire at the end of the season.
The Frenchman has been tight-lipped about his plans in 2015, while Red Bulls head of global soccer Gerard Houllier was quoted as saying Henry could retire, following the club's 1-0 friendly win over Arsenal last month.
And Donovan's announcement to call time on his career at the end of the MLS season - aged 32 - has only raised more doubt about Henry's own future, though the Arsenal icon insisted nothing has been decided.
"Some of my friends are telling me that I still look fit. I don't feel fit after games, though, but it is what it is," Henry told reporters on Friday.
"You have to respect anyone's decision. I said to you, as long as I can run, I will keep on playing.
"Sometimes it's not only down to your body, it's also what's happening up there in your head.
"We'll see. I still feel fresh, somehow, after a lot of games in my career. But I'm okay still so far."
Henry has scored five goals in 19 appearances for the Red Bulls this season, while he starred as the MLS All Stars defeated German champions Bayern Munich 2-1 on Wednesday.
