(CNN) A federal appeals court on Friday said it would not lift an injunction that is blocking the Trump administration's asylum ban from going into effect.

Trump signed a presidential proclamation last month that would bar migrants who illegally cross into the US through the southern border from seeking asylum outside of official ports of entry. But a federal judge in San Francisco temporarily blocked the measure , arguing that it "irreconcilably conflicts" with immigration law and the "expressed intent of Congress."

A panel of judges on the 9th US Circuit Court of Appeals said Friday that the lower court's temporary injunction should remain in place. The majority held that the Trump administration's proclamation is "likely inconsistent with existing United States law."

The temporary restraining order, which is effective nationwide, will remain in place until December 19, when the lower court judge has scheduled another hearing, or further order of the court.

The 9th Circuit panel sympathized at times with some of the government's arguments but said that the law is clear.

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