A US federal judge continued to block a state law that threatened to shut down Mississippi's only abortion clinic and make it nearly impossible for a woman to get the procedure in the state.

US District Judge Daniel P. Jordan III temporarily blocked the law on July 1 and extended that order, though he did not say when he would rule on the clinic's request to put the law on hold for a longer period.

If he grants that request, the case eventually would go to trial.

The US Supreme Court has ruled that American states can't place undue burdens or substantial obstacles to women seeking abortion.

The state law would require anyone performing clinic abortions to be an OB-GYN with privileges to admit patients to a local hospital. The doctors at the clinic in Jackson do not have those privileges, which the clinic has said are not necessary.

Supporters of the law said it is designed to protect patients. Republican governor Phil Bryant has said he hopes it will help make Mississippi "abortion-free".

The clinic, Jackson Women's Health Organisation, said it has been unable to obtain admitting privileges for its two out-of-state OB-GYNs because local hospitals have not responded to their requests.

"They're out to close us down," the clinic's owner, Diane Derzis, said of state officials.

Admitting privileges can be difficult to get because hospitals might not grant them to out-of-state physicians, or hospitals with religious affiliations might not give them to abortion doctors.

When clinic employees called a Catholic hospital to ask about applying for privileges, "We were told not to bother," Ms Derzis said.