Washington(CNN) President Donald Trump on Wednesday started to reshape US immigration enforcement policies via executive action, taking his first steps toward fulfilling some of the most contentious pledges that defined his campaign -- building a border wall and speeding the deportation of undocumented immigrants.

Trump signed two executive orders directing the construction of a wall on the US-Mexico border, boosting border patrol forces and increasing the number of immigration enforcement officers who carry out deportations. The orders also call for stripping sanctuary cities of federal grant funding and announced sweeping new criteria that could make many more undocumented immigrants priorities for deportation.

"Beginning today, the United States of America gets back control of its borders," Trump told employees of the Department of Homeland Security at the department's headquarters in Washington.

But while Trump directed the "immediate construction of a physical wall on the southern border," the executive orders do not cover the cost of the wall. Trump has repeatedly promised that Mexico will reimburse US taxpayers for the construction costs, a suggestion Mexican officials have rejected out of hand.

The president's moves sent alarm bells ringing in immigrant activist circles, where questions had continued to swirl about whether Trump would truly implement many of the hard-line immigration policies he articulated during his campaign.

Trump also indicated he does not need Congress to pass new legislation to implement the border control and immigration reform agenda he outlined during his campaign for president, saying he would "work within the existing system and framework."

"We do not need new laws," Trump said soon after signing the two executive orders.

The executive orders Trump signed Wednesday call for boosting the ranks of Border Patrol forces by an additional 5,000 agents as well as for 10,000 new Immigration and Customs Enforcement officers to carry out deportations. The orders noted that the increases were subject to Congress's appropriation of sufficient funds.

Building the wall

Construction of the wall could begin in months, but planning for the massive project is "starting immediately," Trump said Wednesday in an interview with ABC News.

Trump confirmed his plans to build the wall with federal funds and then seek reimbursement from Mexico, an idea Mexico has rejected. But negotiations, he said, would begin "relatively soon."

"I'm telling you there will be a payment. It will be in a form, perhaps a complicated form," Trump said.

Trump also for the first time appeared to articulate on Wednesday the argument he might make to Mexican officials as he looks to compel them to pay for the wall.

Trump stressed Wednesday that the wall would "help Mexico" by deterring illegal immigration from countries farther South through Mexico.

"We are going to stabilize on both sides of the border and we also understand that a strong and healthy economy in Mexico is very good for the United States," Trump said.

Trump erases doubt about commitment to hardline policies

Trump's actions leave little doubt about whether his immigration policies as president would differ from his campaign rhetoric.

There remained little question, for example, about whether Trump would push to increase deportations of undocumented immigrants. His increases in the number of border patrol and immigration officers -- adding 10,000 immigration officers to an ICE workforce of just 20,000 -- raised the specter of Trump's campaign promise of mass deportations.

One of Trump's executive actions was expected to call for tripling "enforcement and removal operations/agents" of the Immigration and Customs Enforcement agency, which is charged with arresting and deporting undocumented immigrants living in the US. The order also calls for a 5,000-person increase in Customs and Border Protection personnel.

Marielena Hincapié, executive director of the National Immigration Law Center, called Trump's actions Wednesday "extremist, ineffective and expensive" and accused the President of using lies about immigrants to drive US policy.

"Trump is taking a wrecking ball to our immigration system. It shouldn't come as a surprise that chaos and destruction will be the outcome," Hincapié said, adding that her organization has already drafted legal papers to challenge Trump's moves.

And Greisa Martinez, advocacy director at the United We Dream Network, argued that Trump's moves "lay the groundwork for mass deportation."

Trump's executive orders on Wednesday did not address those of his predecessor, former President Barack Obama, which safeguard undocumented immigrants who came to the US as children or who are parents of lawful US residents from deportation. Trump during his campaign signaled he would repeal those orders.

New criteria for deportation priorities

Trump also outlined new criteria for determining which undocumented immigrants should be prioritized for deportation, putting hundreds of thousands and perhaps millions more people at the top of the federal government's list of people to deport.

Any undocumented immigrant convicted or simply charged with a crime that hasn't been adjudicated could be deported under the Trump administration's new policy.

Under Obama, only undocumented immigrants convicted of a felony, serious misdemeanor or multiple misdemeanor were considered priorities for deportation.

New priorities for deportation under Trump also include any undocumented immigrants who abuse public benefits, or simply those considered "a risk to public safety or national security... in the judgment of an immigration officer" -- an entirely open-ended premise.

Trump's hardline immigration rhetoric and policy proposals during the campaign often put him at odds not only with Democrats but with many in his own party who called his proposal to build a wall on the US-Mexico border unnecessary and his calls to deport all undocumented immigrants cruel and unrealistic.

Trump persevered in his hardline rhetoric throughout the campaign, resisting efforts to pivot to a more moderate stance on the issue in the general election despite calls to soften his rhetoric.

Now, his actions on Wednesday took a big first step toward satisfying his political base of support that hitched to his campaign amid Trump's bold promises of building a wall, deporting undocumented immigrants and in the process creating a safer country, despite a total lack of evidence tying undocumented immigrants to higher crime rates.

Trump catapulted his campaign into controversy and relevance with his announcement speech in June 2015, in which he pledged some of the hardline immigration policies he was set to enact and decried undocumented immigrants as criminals and "rapists." Trump never apologized for those comments.