Vermaelen played the full 90 minutes of Belgium's friendly in Greece on Wednesday against the advice of the Gunners. Van Persie, meanwhile, played 45 minutes for Netherlands against England despite suffering a groin injury in training 24 hours earlier.
"It looks like Belgium has made a decision which I still do not understand and we will look to see if we can put a complaint in,'' Wenger said. "Firstly they forced the player to travel, then they forced him to play 90 minutes after being injured and had a centre-back on the bench who did not play at all, in a friendly game knowing they do not even go to the European Championship. For me, that is difficult to understand.
"The friendlies are becoming more and more difficult to accept for everybody. I was always in favour of using the players for official games and I never asked any player not to go 100% for his country when it is a qualifier or a big competition, but the friendlies are becoming more and more difficult, especially in this period.
"For us it is vital we do not lose the players now. If you go into a period like that with players already touched (by injury) you have more chances to lose the players.
"The Holland manager (Bert van Marwijk) hasn't spoken to me, but he knew Robin was injured because he said despite his groin problem, he will play him, it is the same with the Belgium manager (Georges Leekens).
"We are the only team in the world who had that schedule so it is very difficult to understand that our players had to go injured to Greece and play 90 minutes for Belgium. That's frankly not defendable. It is disrespectful to the players as well as me.''
With four games in ten days, Wenger was hesitant to confirm that Van Persie will feature at Anfield.
"It's difficult to say because we are before training. If it was after training I could give a better view," Wenger said. "It is vital we don't lose players.
"We played Sunday against Tottenham, Wednesday was international friendlies, Saturday we're 12.45 at Liverpool and then Tuesday against Milan. Any footballer knows that's impossible."
"Tomas has also got a groin problem but I think he will play," Wenger said. "Aaron Ramsey is out for Saturday and out for Tuesday. It is too early for him, he has no chance for the weekend. He will be out for Milan as well. Earliest will be Newcastle. However, Diaby is available again."
Wenger knows the difficulties of playing at Anfield, where Liverpool are often inspired by their home support. The Arsenal boss called on his men not to hide this weekend.
"They are a team who is fighting for the Champions League places as well, which is why it's vital for us," he said. "At home they've won only four games, so they've faced many teams who have defended well against them.
"I have a big respect for that crowd and the way they are behind that team, so you need to be prepared for a game of big pace, big drive, and you cannot hide."