President-elect Donald Trump is readying a blitz of executive orders that he plans to issue just hours after he is sworn into office , wielding his executive authority on day one to push forward his top priorities related to the border, energy and government reform.

The breadth of the orders, which would make major changes to immigration, energy and government hiring policies, illustrates the urgency with which Trump and his team plan to launch into an ambitious agenda.

Stephen Miller , Trump’s incoming White House deputy chief of staff for policy, briefed a small number of senior GOP leaders Sunday afternoon about the administration’s plans. They include declaring a national emergency on the U.S.-Mexico border, rescinding Biden administration directives on diversity, equity and inclusion and unwinding President Biden’s limits on drilling offshore and on federal land, Miller told the lawmakers, according to Capitol Hill Republicans briefed on the call.

Part of Trump’s efforts to overhaul the federal government will be aimed at rewriting hiring rules for employees and creating a new process for firing others. The president-elect will again sign an executive order, known as Schedule F, which he issued in October 2020 to eliminate job protections for federal workers, the Republicans said. The Biden administration had previously blocked the order.

Trump’s transition team didn’t immediately respond to a request for comment.

The orders, which bypass Congress, are expected to be “border heavy” and focus on undoing the executive orders issued by Biden when he first came to office in 2021, according to a Republican familiar with the planning.

Trump is expected to declare a national emergency on the border, Republicans briefed on the call said, which would in turn unlock additional Pentagon funding and assets to help address the matter. He is also expected to order troops to help build more infrastructure at the border. The president-elect will direct his administration to relaunch a policy known as Remain in Mexico, which requires migrants seeking asylum at the southern border to live in northern Mexican border cities during their U.S. court proceedings.

Trump also plans to designate cartels as foreign terrorist organizations and restrict entry to the U.S., likely through a travel ban. It couldn’t immediately be learned how any travel ban might work.

Besides the border-focused immigration orders, Trump’s advisers have also been planning immigration raids in several major cities during the first few days of the new administration, according to people familiar with the discussion. The cities that are expected to be targeted include Chicago , Boston, Washington, D.C., Miami, Los Angeles, Denver, New York and San Antonio. The scale of the raids and the number of cities that will see increased enforcement activity remains in flux.

Miller also discussed what he called an “energy-omnibus,” with the Trump aide describing a wide-ranging directive that would declare a national energy emergency, according to one of the Republicans on the call. Trump would also move to terminate Biden-era restrictions on drilling and policies promoting electric vehicles, while calling for cutting spending on efforts to address climate change.

Write to Olivia Beavers at Olivia.Beavers@wsj.com and Tarini Parti at tarini.parti@wsj.com