对，就是新加坡的美国大使馆的规定。
There are two ways to apply for a visa from the U.S. Embassy: travel-agency
submissions and mail-in submissions (for Singapore residents only). We do n
ot accept walk-in non-immigrant visa applications. You should only come in p
erson after you have received a written invitation for an interview or if yo
u have applied within the last year and were invited to bring more informati
on.
以上是引自大使馆的网页 http://singapore.usembassy.gov/consular/NIV/nonimmigrant_HowToApply.shtml
