The supreme court will not let the Trump administration begin enforcing a ban on asylum for immigrants who illegally cross the US-Mexico border, a key component of policies meant to make it harder for immigrants to enter and stay in the United States.

New justice Brett Kavanaugh and three other conservatives on the nine-member panel sided with the administration. But the court’s order, issued on Friday, left in place lower-court rulings that blocked Donald Trump’s proclamation in November automatically denying asylum to people who enter the country from Mexico without going through official border crossings.

Trump said he was acting in response to caravans of migrants making their way to the border. The administration complained that the nationwide order preventing the policy from taking effect was too broad.

But chief justice John Roberts and the court’s four more liberal justices rejected the administration’s suggestion for narrowing it.

San Francisco-based US district judge Jon Tigar blocked the policy on 19 November. The San Francisco-based 9th US circuit court of appeals then refused the administration’s request to lift Tigar’s order.

Trump criticised Tigar, leading to an extraordinary rebuke by Roberts, who defended the independence of the federal judiciary and wrote in a public response to Trump: “We do not have Obama judges or Trump judges, Bush judges or Clinton judges.”

The administration has sought ways to block thousands of Central American men, women and children traveling in caravans to escape violence and poverty in their home countries from entering the US, with Trump calling the people in the caravans a national security threat.

Trump’s proclamation stated that mass migration on the border had precipitated a crisis and he was acting to protect the national interest. His policy was crafted to alter American asylum laws that have given people fleeing persecution and violence in their homelands the ability to seek sanctuary in the US.