The US says a purported confession from a prominent Chinese lawyer on state television runs counter to the rule of law.
Zhang Kai admitted to various crimes including disturbing social order in a broadcast on Thursday.
He has been helping defend Christians resisting government orders to remove crosses from buildings.
China says it guarantees religious freedom but there are concerns about a crackdown on Christian activities.
On Friday a pastor was jailed for refusing to remove a cross from his church’s roof.
The authorities have justified the tearing down of crosses by saying they break planning rules.
Zhang Kai was arrested last year shortly before a planned meeting with the US envoy on religious freedoms.