The statement by the U.S. embassy in Baku came after some 200 government supporters tried to storm the headquarters of the opposition Popular Front party today amid growing tensions ahead of the November polls.
Most of the group were from the Muasir Musavat party and said they were angry over the opposition party's alleged connections to Armenian agents.
Ruslan Basirli, the leader of the opposition youth movement Yeni Fikir, which is believed to have links to the Popular Front, was arrested last week and charged with allegedly accepting Armenian money to finance a revolution in Azerbaijan. Yeni Fikir denies the accusation.
There have been several clashes between pro-government supporters and opposition members in the last few days.