President Donald Trump delivers remarks during a meeting with Speaker of the House Paul Ryan, Senate Majority Leader Mitch McConnell (R), Chairman of the Senate Finance Committee Orrin Hatch, other members of congress and his administration regarding tax reform in the Roosevelt Room of the White House on September 5, 2017 in Washington, DC.

President Donald Trump on Thursday claimed that about 800,000 young people protected from deportation under an Obama-era program "have nothing to worry about" during the six-month delay period before the policy ends.

"No action!" Trump wrote in a tweet.

Trump: For all of those (DACA) that are concerned about your status during the 6 month period, you have nothing to worry about - No action!

House Democratic Leader Nancy Pelosi said she spoke to Trump on the phone on Thursday and urged him to make clear that the six-month window "is not a period of roundup" that would make people protected by the program "vulnerable." Then, "boom, boom, boom, the tweet appeared," she added.

On Tuesday, the Trump administration announced it would rescind the Deferred Action for Childhood Arrivals program, with a six-month delay to allow for Congress to try and convert the program into law. Attorney General Jeff Sessions and Trump argued that the Obama administration did not have the authority to implement DACA.

The program gives certain children of immigrants who came to the country illegally a two-year period of protection from deportation and allows them to work in the United States.

Trump later tweeted that he would "revisit" the program if Congress cannot "legalize" it in six months.

Pelosi claimed that Trump on Wednesday said he would sign the DREAM Act — legislation that would shield the people protected by DACA. It has previously failed to pass the GOP-controlled Congress.

While Trump appears to be referring to deportation with his tweet, his administration will begin what it calls an "orderly wind down" of the program during the six-month period. Here's what the Trump administration is doing, according to the Department of Homeland Security:

Acting DHS Secretary Elaine Duke has issued a memo formally rescinding DACA and starting the "orderly wind down."

The government will not process any new applications or requests for DACA protection.

People currently protected will not be affected before March 5, "so Congress can have time to deliver on appropriate legislative solutions," according to Duke.

Current DACA holders' work permits and protection from deportation remain in effect until they expire, at which time they will no longer be shielded. The government will hear all pending applications for DACA protection and renewals and decide on them on a case-by-case basis.

Trump's tweet Thursday came a day after he agreed to a short-term debt ceiling and government funding deal with Pelosi and Senate Minority Leader Chuck Schumer, over the objections of Republican congressional leaders.