An official in the US state of Arizona has quit months after being charged with running a human smuggling operation.

The set up paid pregnant women from the Marshall Islands to give up their babies in the US.

Paul Petersen's resignation comes after months of pressure from his bosses in Maricopa County in Phoenix.

According to the indictment, he is a licensed attorney who practices law in Arizona, Utah and Arkansas.

Beginning in 2014, Petersen devised a scheme to defraud and obtain money and property from unknowing adoptive parents and others.

He is accused of illegally paying women from the Pacific island nation to travel to the US to give up their babies in at least 70 adoption cases in Arizona, Utah and Arkansas over three years.

Citizens of the Marshall Islands have been prohibited from traveling to America for adoption purposes since 2003.

Petersen is accused of human smuggling in Utah and Arkansas and defrauding Arizona's Medicaid system by US$800,000 (€717,451) by submitting false applications for the women to receive state-funded health coverage.

Authorities say the women who went to Utah to give birth received little to no prenatal care.

They also said Petersen and his associates took passports from the pregnant women while they were in the US to assert more control over them.

Petersen has pleaded not guilty to the charges in Arizona and Arkansas. He has not yet entered a plea in Utah.

Lynwood Jennet, who was accused of helping Petersen in the scheme, pleaded guilty last month in Arizona to helping arrange state-funded health coverage for the expectant mothers, even though the women did not live in the state.

She has agreed to testify against Petersen.