US officials sent “high-level” requests in July and August to Indonesia’s defence and foreign ministers. However, Indonesia’s President Joko Widodo refuted the help.
The request comes as tensions between US and China mount over their influence in Southeastern Asian territories.
Indonesia has a long-standing neutral stance to avoid entering conflict.
It does not allow foreign defence forces to operate within its boundaries.
The country does not officially claim the disputed South China Sea territory, but observes part of it as its own.
It has frequently expelled Chinese coastguard boats and fishing vessels from a sector of the territory.
However, its economic links to China mean it has to remain in peaceful terms with Beijing.
In an interview conducted in early September, Indonesia’s Foreign Minister Retno Marsudi said: “We don’t want to get trapped by this rivalry.
“Indonesia wants to show all that we are ready to be your partner.”
All 10 nations were advocating for peace and staying out of troubles between the two superpowers.
She said: “ASEAN has a good culture, but we have to nurture it.
“We can’t take it for granted that these values will live forever.”
Dino Patti Djalal, a former Indonesian ambassador to the US, said the “very aggressive anti-China policy” of the US had sparked concerns in Indonesia.
Speaking to Reusters, he said: “It’s seen as out-of-place. We don’t want to be duped into an anti-China campaign.