Homeland Security Secretary John Kelly has signed sweeping new guidelines that empower federal authorities to more aggressively detain and deport illegal immigrants inside the United States and at the border.

In a pair of memos, Kelly offered more detail on plans for the agency to hire thousands of additional enforcement agents, expand the pool of immigrants who are prioritized for removal, speed up deportation hearings, and enlist local law enforcement to help make arrests.

Immigrant rights advocates said the two memos signed by Kelly mark a major shift in US immigration policies by dramatically expanding the scope of enforcement operations.

A White House official said the memos were drafts and that they are under review by the White House Counsel’s Office, which is seeking some changes. The official, who spoke on condition of anonymity because the process is not complete, declined to offer specifics.

The new directives would supersede nearly all of those issued under previous administrations, Kelly said, including measures from President Obama aimed at focusing deportations exclusively on hardened criminals and those with terrorist ties.

‘‘The surge of immigration at the southern border has overwhelmed federal agencies and resources and has created a significant national security vulnerability to the United States,’’ Kelly stated in the guidelines.

He cited a surge of 10,000 to 15,000 additional apprehensions per month at the southern US border between 2015 and 2016.

The memos do not include measures to activate National Guard troops to help apprehend immigrants in 11 states that had been included in a draft document leaked to reporters Friday. DHS officials said Kelly, whose signature did not appear on that draft document, had never approved such plans.

The new procedures would allow authorities to seek expedited deportation proceedings, currently limited to undocumented immigrants who have been in the country for two weeks or fewer, to anyone who has been in the country for up to two years.

Another new provision would be to immediately return Mexican immigrants who are apprehended at the border back home pending the outcomes of their deportation hearings, rather than house them on US property, an effort that would save detention space and other resources.

The guidelines also aim to deter the arrival of a growing wave of 155,000 unaccompanied minors that have come from Mexico and Central America over the past three years. Under the new policies, their parents in the United States could be prosecuted if they are found to have paid smugglers to bring the children across the border.

‘‘This memo [is] just breathtaking, the way they really are looking at every part of the entire system,’’ said Marielena Hincapié, executive director of the National Immigration Law Center.

The memos leave in place one important directive from the Obama administration: a program called Deferred Action for Childhood Arrivals that has provided work permits to more than 750,000 immigrants who came to the country illegally as children.

Trump had promised during his campaign to ‘‘immediately terminate’’ the program, calling it an unconstitutional ‘‘executive amnesty,’’ but he has wavered since then. Last week, he said he would ‘‘show great heart’’ in determining the fate of that program.

The memos instruct agency chiefs to begin hiring 10,000 additional ICE agents and 5,000 more for the Border Patrol, which had been included in Trump’s executive actions.

Kelly also said the agency will try to expand partnerships with municipal law enforcement agencies that deputize local police to act as immigration officers for the purposes of enforcement. The program was signed into law by the Clinton administration and grew markedly under President George W. Bush’s tenure. It fell out of favor under the Obama administration.

Currently, 32 jurisdictions in 16 states participate in the program, according to Kelly’s memo.

In a series of executive actions in January, President Trump announced plans to make good on his campaign promises to build a wall on the border with Mexico and to ramp up enforcement actions against the nation’s estimated 11 million unauthorized immigrants.

Kelly’s memos, which have not been released publicly, are intended as an implementation blueprint for DHS to pursue Trump’s goals.

A Department of Homeland Security spokeswoman declined to comment on the documents but did not dispute their authenticity.