President Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE on Wednesday praised White House adviser Stephen Miller while insisting that the top aide is not driving the administration's immigration agenda.

“Stephen is an excellent guy. He's a wonderful person. People don't know him. He's been with me from the beginning,” Trump told reporters as he departed the White House for a trip to Texas.

“Frankly, there’s only one person that's running it," Trump added. "You know who that is? It's me."

ADVERTISEMENT

Miller, a former Senate aide who has pushed for hard-line immigration policies in the Trump administration, has emerged as a key player amid rapid turnover at the Department of Homeland Security (DHS).

He reportedly pushed for the ouster of departing DHS Secretary Kirstjen Nielsen Kirstjen Michele NielsenDHS IG won't investigate after watchdog said Wolf, Cuccinelli appointments violated law Appeals court sides with Trump over drawdown of immigrant protections Democrats smell blood with new DHS whistleblower complaint MORE, and has lobbied for other changes at the agency that oversees immigration enforcement, terrorism prevention, cybersecurity and other areas.

GOP senators this week raised concerns about Miller's growing influence at the White House, particularly on immigration and border security policies.

Sen. Chuck Grassley Charles (Chuck) Ernest GrassleyCollins says she will vote 'no' on Supreme Court nominee before election The Hill's Morning Report - Sponsored by Facebook - Trump, GOP allies prepare for SCOTUS nomination this week Gardner signals support for taking up Supreme Court nominee this year MORE (R-Iowa) is among those who have cautioned the president against making further personnel changes at DHS. He urged Trump not to get rid of U.S. Citizenship and Immigration Services Director Lee Francis Cissna, who is said to be in Miller's crosshairs.

The shakeup at DHS comes as the administration is considering a range of polices that would clamp down on the influx of migrants at the southern border.

"I think that the whole asylum rules, laws and regulations have been taken advantage of by people that are very bad people in many cases," Trump said Wednesday, calling on congressional Democrats to pass legislation to close loopholes.

Trump said Tuesday he is not looking to bring back the widely criticized practice of separating families who cross the border illegally.

However, a senior administration official said the White House is looking at ways to make it harder for migrants crossing into the U.S. through Mexico to receive asylum, in part by forcing them to meet stricter requirements proving they have a credible fear of returning to their home countries.

The president in recent weeks has approached border security with renewed intensity. He threatened to close the U.S.-Mexico border, rescinded his nominee to lead Immigration and Customs Enforcement, vowing he wanted to go in a "tougher direction, and appointed Customs and Border Protection (CBP) chief Kevin McAleenan as acting DHS secretary.

CBP announced Tuesday that agents apprehended more than 92,000 individuals in March trying to cross the southern border, the highest monthly tally this year and more than double the number of apprehensions reported in March 2018.

Updated at 10:40 a.m.