Pushing back on Trump, all Senate Democrats now back bill to stop family separations GOP senator on border separations: This is "not the right thing to be doing."

Senate Democrats are pushing back on President Donald Trump's false attack that they're to blame for immigrant children being separated from their parents, saying Monday all 49 of them now have signed on to new legislation that would halt the practice.

Sen. Joe Manchin of West Virginia became the 49th Democrat to sign on to the legislation on Monday.

"As a father, grandfather, and Christian, I am wholeheartedly opposed to any policy that allows innocent children to be separated from their parents as they enter our country," Manchin said in a statement.

The Senate's second-ranking Republican, John Cornyn of Texas, said he too opposes the practice and said he plans to re-introduce legislation that would "mitigate the problem of family separation while improving the immigration court process for unaccompanied children and families apprehended at the border."

"We have to keep family members together and prevent unnecessary hardship, stress, and outrage," Cornyn said. "The good news is we have it within our power to find a better way because parents who are awaiting court proceedings shouldn't have to do so separated from their children, and children shouldn't be taken from their parents and left frightened and confused about where they are and what is transpiring around them."

Another Texas Republican, Ted Cruz, said he would introduce "emergency legislation to keep immigrant families together."

Alaska Republican Lisa Murkowski said, “The time is now for the White House to end the cruel, tragic separations of families," in a statement. "To blame previous administrations for a wrong committed today is not acceptable. The Attorney General and Secretary of Homeland Security should make the call today. If the administration does not fix this and fast, we in Congress must,” she said.

And Arizona Republican John McCain tweeted that "The administration's current family separation policy is an affront to the decency of the American people..."

Also weighing in on the controversy: Senate Chaplain Barry Black.

Black is the 62nd chaplain of the Senate and the first African-American person to hold the position. Black acts as a spiritual adviser and counselor to senators, their families, and staff.

"As children are being separated from their parents, remind us to love our neighbors as ourselves and to protect the most vulnerable in our world," Black said during his daily prayer on the Senate floor.

Notably, the Office of the Chaplain is nonpartisan, nonpolitical, and nonsectarian.

Sen. Kamala Harris, a California Democrat, went a step further Monday afternoon by calling on Department of Homeland Security Secretary Kirstjen Nielsen to resign.

"It's time for Secretary Nielsen to resign. The government should be in the business of keeping families together, not tearing them apart. And the government should have a commitment to transparency and accountability. Under her tenure, DHS does not have a track record of either," Harris said in a statement.

President Trump has put the blame for the policy squarely on Democrats, claiming they're blocking his immigration reform legislation that he says would end family separation. On Monday, he tweeted: “It is the Democrats fault for being weak and ineffective with Boarder (sic) Security and Crime. Tell them to start thinking about the people devastated by Crime coming from illegal immigration. Change the laws!”

The White House on Monday sent a memo to congressional Republicans with talking points aimed at hitting Democrats on the issue.

"Congressional Democrats’ slavish support for open borders has created a humanitarian crisis at our border where criminal organizations smuggle hundreds of thousands of children across international boundaries, subjecting the children to unimaginable suffering and misery," the memo reads.

In another talking point, the memo asks why Democratic lawmakers and members of the media "believe illegal aliens are entitled to more rights than those afforded to American citizens."

The Senate’s top Democrat, Chuck Schumer of New York, hit back and said if Trump wanted to change the policy, he could do it without congressional help.

“As everyone who has looked at this agrees, this was done by the president, not Democrats. He can fix it tomorrow if he wants to, and if he doesn’t want to, he should own up to the fact that he’s doing it,” Schumer said in a statement.

Amid growing criticism of the Trump administration’s “zero tolerance” policy, Republicans in Congress are also now demanding answers, despite DHS insistence that there is no policy aimed at separating families.

“Contrary to what DHS has indicated as proper procedure, we are currently seeing cases where immigrant families seeking asylum are separated after lawfully presenting themselves at a U.S. port of entry. I believe DHS ought to respond to valid questions concerning asylum processing, including any policies pertaining to the separation of families,” Sen. Jeff Flake, R-Ariz., said in a statement.

Flake and Sen. Susan Collins, R-Maine, fired off a letter to the Departments of Homeland Security and Health and Human Services secretaries, Kristjen Nielsen and Alex Azar, seeking information regarding their respective departments' policies and procedures when migrant families approach legal U.S. ports of entry seeking asylum.

In the letter, Flake and Collins note Nielson’s recent appearance before members of the Senate for a hearing during which she testified that “immigrant parents and children who present themselves at U.S. ports of entry to request asylum will not be separated.”

Despite her testimony, DHS announced last week that between April and May this year, nearly 2,000 children have been separated from their parents at the border.

“Ensuring the safety and security of young children is a longstanding priority of the American legal system. In asylum cases, it is especially important to keep families together when neither the child nor the parent has violated any laws,” Flake said.

On CBS’ Face the Nation on Sunday, Collins blasted the administration for the trauma children are faced with when they are separated from their parents.

“What the administration has decided to do is to separate children from their parents to try to send a message that if you cross the border with children, your children are going to be ripped away from you,” she said. “That is traumatizing to the children who are innocent victims and it is contrary to our values in this country.”

Sen. Orrin Hatch, R-Utah, on Monday said that members of Congress must forge ahead to find an immigration solution that is both bipartisan and compassionate.

“I am working with colleagues in both houses on a path forward that recognizes the need for compassion for children and families without incentivizing illegal border crossings. That solution can and should be bipartisan,” Hatch said in a statement.

In an interview with conservative radio host Hugh Hewitt, GOP Sen. Pat Toomey of Pennsylvania admitted that he didn’t know much about the impact of the administration’s policy, but he went on to say the separations are not the “right thing to be doing.”

“This is not my area of expertise, Hugh. I’m going to have to drill down into this and address it,” he said. “And maybe you’re right. Maybe this is happening with a higher frequency than I’ve been aware of, and it is certainly, it’s just not the right thing to be doing,” Toomey said.

On Monday, House Democratic Minority Leader Nancy Pelosi spent the day in San Diego County touring several of the area’s immigration detention facilities with several other members of Congress.

"This is not about immigration, this is about humanity," Pelosi said, adding that Democrats have zero tolerance for family separations.

Over the weekend, a group of Democratic lawmakers toured an immigration detention facility in New Jersey and met with detained asylum seekers who have been separated from their families.

"Today, on Father’s Day, we spoke to fathers whose children have been ripped from their arms, who have no idea when or if they will see their children again," Rep. Jerrold Nadler said during a press conference with reporters after the surprise visit.

The House Judiciary Committee Ranking member led the group of seven lawmakers — including Reps. Frank Pallone and Bill Pascrell of New Jersey, and Reps. Albio Sires, Carolyn Maloney, Hakeem Jeffries and Adriano Espaillat of New York — for the excursion to the Elizabeth Contract Detention Facility in New Jersey.

In an interview with ABC News, Rep. Frank Pallone of New Jersey described his meeting with a father who doesn’t know where his five-year-old daughter is after they were separated at the border.

“The typical one was from Central America, and he came with his daughter who was about five,” Pallone said. “And you know he doesn't know where she is. He has heard that she may be in Michigan but there's no process for telling these fathers or parents where their children are.”

Pallone said many of the families are from rural towns and are seeking political asylum.

“In other words, they didn't come here for economic reasons because they're looking for a job,” Pallone said. “They came here because they were fleeing persecution.”

ABC News’ Kendall Karson and Ben Siegel contributed to this report.