Midfielder Wilshere has not played since the defeat at Tottenham on March 3 after he was rested because of an ankle problem, and had been initially expected to feature this weekend against Reading following a rehabilitation schedule which included a trip to Dubai.
However, Wenger revealed this morning that Wilshere would not be rushed back into action, while forward Theo Walcott is also set for more treatment on what was described as a "minor hip/groin injury" picked up training with England ahead of the San Marino World Cup qualifier.
"Wilshere's injury is not better or worse. It was an inflammation of his [ankle] bone and we had such history with him [that] we are a bit more cautious than we would be with you or with me," said Wenger.
"We deferred a little bit his rehab by one week. We gave him one more week rest because it was wise medically to do it.
"Honestly, it's very difficult [to say when he will be back]. I believe in two weeks on Sunday, that means not the next game, the game after."
Wenger insisted that given Wilshere's injury record, having been sidelined for more than a year with a different ankle problem, the club's medical staff would take no chances.
"We will rest him when it is needed. He has regular scans and as soon as we have an alert we will respect it no matter what is at stake," Wenger said.
"Jack had a difficult moment of course when you told him because he didn't feel any special pain, but he knows he has to take care of his future. because he is a very young player, I think he accepts it."
Arsenal also saw midfielder Alex Oxlade-Chamberlain away with England, scoring in the 8-0 rout of San Marino.
Wenger maintains he has no issue with the way his players are utilised in the World Cup qualifiers.
"I have no conversation with the (England) manager, especially when it's a competitive game. When they fight for points, he uses the players like he wants to. I don't interfere in that," Wenger said. "When it's a friendly, you try to influence a bit in your favour when it's needed. I believe that every manager does that.
"It is more communication between the two medical departments because you have to send the player away who is already half injured, but still plays.
"We have a good relationship (with England) and I have no concern about that. Walcott's (injury) is an accident that could have happened here."
Arsenal will check on the fitness of full-back Kieran Gibbs (flu) and midfielder Abou Diaby (knee) ahead of Saturday's visit of the Royals, who will continue their battle against relegation under new boss Nigel Adkins.
Wenger knows with just four points separating Arsenal from fourth-placed local rivals Tottenham, there is no more room for error if they are to get back into the Champions League places.
"We just want to continue our form. Bayern and Swansea is a good inspiration to continue our run-in," Wenger said.
"There are nine games to go. We play five at home and four away. With the form we have shown at Bayern and at Swansea, I think we have a very good chance to finish in the top four."