The Chilean has less than a year remaining on his current Gunners deal and is yet to sign fresh terms to stay at the club, meaning that he could potentially leave on a free next summer.
Sanchez is thought to be a transfer target for Premier League rivals Manchester City, but Wenger says that he wants to keep the 28-year-old for the forthcoming season and that his decision "is clear".
"Yes, the board supports me to make the decisions on a technical front," Wenger told Sky Sports News. "I can tell you is that he is focused, and my decision is clear - he will stay and he will respect that. It is as simple as that.
"Every negotiation has to be a little bit secret. The transparency of society is very pushy but we have to resist a little bit, as much as we can. I think he will be here this season, and if we can do it for more seasons we will do it as well."
Arsenal have reportedly offered Sanchez a new contract worth £290,000 a week.