About "ALTER USER" command

Good day for You.

I need to change password of the usuary POSTGRES using the commando "ALTER
USER". This change I must do it by means of a program .bat in “quiet” way.

I have the following instruction in .bat program :

psql -S "ALTER USER postgres WITH PASSWORD 'xxtyod';"

But when I execute this program, it requests user password to me.

It is possible that some commando exists who is due to place before so that
he does not request ANY password.

then, it would be thankful indicated to me what commands is used so that it
does not request any type of password nor of user. Solely that executes the
instruction that I mentioned to them previously.

Again, thanks for its valuable collaboration.

Sincerely ,