He did not immediately provide details of the bill, but said that it resolves the issue of so-called Dreamers, undocumented adult migrants who entered the USA as children, "in a very elegant way".
Technically, the president did not have to sign an executive order to stop the separation, according to our Spectrum News Networks team in Washington, DC. "Separating - especially very small children from their parents at the border is not something we should do".
Both Republican bills in the House, which Democrats and immigration advocacy groups have blasted, would fund Trump's border wall and reduce legal migration, in part by denying visas for some relatives of USA residents and citizens who are living overseas, sometimes referred to as "chain migration".
There has been an increase in the number of migrant children being separated from their parents as a outcome of the new "zero tolerance" policy for illegal border crossings, according to The Associated Press.
"Congress and the courts created this problem, and Congress alone can fix it", Nielsen said Monday.
Sen. Pat Roberts, R-Kansas, one of 13 Senate Republicans who signed a letter urging Trump to end his administration's separation policy, was also waiting on the yet-unknown details.
Trump had tweeted earlier Wednesday, "It's the Democrats fault, they won't give us the votes needed to pass good immigration legislation".
Videos of youngsters in cages and an audiotape of wailing children had sparked anger in the United States from groups ranging from clergy to influential business leaders, as well as condemnation from overseas, including Pope Francis. The policy has separated a reported 2,400 children from their families since late 2016. The new order means that immigrant families will still be prosecuted for entering the country illegally, though now they will be detained together "indefinitely" at facilities that still may need to be built, as The New York Times reports.
Speaking at a business convention, Trump said children have to be taken away if their parents are jailed for illegally crossing the USA border.
Critics argue it is inhumane for the Trump administration to use children as political pawns.
It's unclear whether the president is supportive of the measure. They want open borders, which breeds frightful crime.
But others pushed back on the idea that Homeland Security had led the rollback.