US adoptions of Russian children have been halted, a week after a Russian boy was rejected by his adoptive mother in the American state of Tennessee.

The Russian foreign ministry said the move would apply until a bilateral adoption agreement could be signed, the BBC reported.

An international outcry erupted last week when the adoptive mother, a nurse, sent the seven-year-old Russian boy on a one-way flight to Moscow on his own.

She sent a note with him saying the boy had psychological issues.

"To Whom It May Concern," the letter read. "This child is mentally unstable. He is violent and has severe psychopathic issues. I was lied to and misled by the Russian orphanage workers and director regarding his mental stability and other issues."

Torry Hansen, 33, reportedly adopted the boy from Russia's Far Eastern town of Partizansk last September.

More than 1 800 Russian children were adopted in the US last year, according to Russia's health and education ministry.