Editor's Note: Read complete updates about President Trump's executive order here.

President Trump and his administration have spent the last week publicly and relentlessly defending the administration's "zero-tolerance" policy that has caused the separation of children from their parents at the southern border.

So it caught Capitol Hill off guard when on Tuesday the president indicated he would be signing an executive order to end family separation, CBS News correspondent Ed O'Keefe reports. Two senior aides tell O'Keefe GOP leadership had no formal heads up from the White House.

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So, what caused or at least contributed to Mr. Trump's decision to reverse course?

"The pressure is everywhere," one senior Republican aide, granted anonymity to speak frankly about party dynamics, told O'Keefe. "The TV is pressure. Bill O'Reilly said this is awful."

Mr. Trump is an avid watcher of cable news, which has been consumed coverage of the family separation policy and images of the government's facilities for children. O'Reilly, the former Fox News host fired over sexual harassment allegations and a friend of the president, made several critical statements about the policy.

"The Trump administration will not win on this one and it should reverse course today," O'Reilly tweeted earlier this week.

The senior aide also said critical comments made by GOP senators who are typically allies of Mr. Trump, such as Sen. Orrin Hatch, R-Utah, also played a role. Hatch and 12 other GOP senators, including Sen. Lamar Alexander of Tennessee, co-signed a letter to the Justice Department Tuesday asking the administration to pause the separation policy until Congress can address the issue.

Other Republican senators with long ties to federal homeland security agencies they oversee also reached out to leaders of those entities to quietly urge them to reverse course.

But Mr. Trump is also urging Congress to pass "comprehensive" immigration legislation to fix border security, as he had before announcing the executive order. And, as CBS News correspondent Paula Reid reports, the executive order is not expected to reverse the "zero-tolerance" policy on prosecuting all illegal border crossings, but it is expected to allow families to be held together during process of prosecution and deportation.