President Donald Trump delayed the planned signing of a directive on cybersecurity Tuesday afternoon as White House staff stepped up attention to legal challenges against his immigration executive orders.

Administration discussions of a lawsuit San Francisco officials filed challenging a Trump order to withhold funds from so-called sanctuary cities complicated the president’s schedule on a busy day in which he also plans to announce his Supreme Court nominee, a White House aide said. Critics dubbed as sanctuary cities municipalities that have adopted a policy of protecting undocumented immigrants by not prosecuting them for violating federal immigration laws.

The aide, who requested anonymity to candidly discuss the reason for the delay, said the administration hasn’t yet determined when it can reschedule the cybersecurity order signing.