The Colombia international did not feature for his national team in their recent wins over United States and Slovenia, but he was quick to stress it was not due to a recurrence of his knee problems.
Falcao missed the latter part of last season at Monaco due to a torn cruciate ligament , which also ruled him out fo the World Cup and hampered his first few weeks at Old Trafford following his loan move in August.
On Thursday, Van Gaal told a media conference the striker, who has not featured for United in a month, will also sit out upcoming fixtures against Arsenal and Hull City.
Meanwhile, while the 28-year-old told the club's official website he is itching to get back to first-team action.
"I am getting better, I feel well and I hope to come back to the pitch soon," he said. "It is disappointing that I can't play but I have to be calm and recover because that is important to help the team when I return to the games."
Some media reports had claimed Falcao had suffered a recurrence of his previous knee injury, something which annoys the striker.
He added: "It is a bit frustrating. Well, it is more than frustrating actually and it detracts from the credibility of the media that there is so much speculation and that so many falsehoods have been written about it.
"I think with an audience of so many millions of people, it is not right. I did take a small injury to my calf, which is something that I need to be careful with, but there are a lot of stories circulating that are pure speculation."
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