"This extension will allow the court sufficient time to evaluate Mr. Armstrong's amended complaint," Tim Herman, a lawyer representing Armstrong, said in a statement.
Armstrong filed an 80-page lawsuit on Monday aimed at halting the agency's case against him, but it was dismissed later that day. The lawsuit was refiled with changes on Tuesday.
The anti-doping agency said it gave Armstrong the extension until the lawsuit or any preliminary injunction is ruled upon.
"USADA believes this lawsuit, like previous lawsuits aimed at concealing the truth, is without merit," USADA chief executive officer Travis Tygart said in a statement.
The charges against Armstrong, if found true, could lead to penalties that could invalidate his Tour de France victories and ban him from the sport for life.
The new deadline for Armstrong to answer the charges is August 13.