By Eli Watkins, CNN

(CNN) -- Texas Democratic Rep. Beto O'Rourke on Sunday railed against the Trump administration separating children from parents at the border, but said responsibility for what is happening is on everyone.

"This is inhumane," O'Rourke said on CNN's "State of the Union." "I'd like to say it's un-American, but it's happening right now in America. And it is on all of us, not just the Trump administration. This is on all of us."

The Department of Homeland Security said Friday that the government had separated about 2,000 children from parents at the border since implementing a policy that results in such family separations.

O'Rourke said he was planning to march to Tornillo, Texas, where the government is holding unaccompanied immigrant children, and several other Democratic lawmakers are due to visit immigration centers in South Texas.

O'Rourke said the march was an effort to drum up enough "outrage" and "public pressure" to change the policy, which Trump suggested is a negotiating tool and has falsely asserted is the fault of Democrats.

In his CNN interview, O'Rourke pledged to introduce a measure in the coming days to end family separation and predicted support from the public.

"I'm confident that the American people this time are going to get it right," O'Rourke said.

O'Rourke also noted that the policy meant children would spend Father's Day uncertain when they would next see their parents.

"At the moment that they finally thought they had reached safety, refuge, were going to petition for asylum, they were taken from their parents, and are now in Tornillo with no idea when or if they will see their mothers or their fathers on this Father's Day again," O'Rourke said.

Former Democratic President Bill Clinton tweeted a similar point on Sunday.

"On this Father's Day I'm thinking of the thousands of children separated from their parents at the border. These children should not be a negotiating tool. And reuniting them with their families would reaffirm America's belief in & support for all parents who love their children," Clinton tweeted.

Kellyanne Conway, a senior aide to Trump, said on NBC's "Meet the Press" that "nobody likes seeing babies ripped from their mother's arms" and that she did not "want anybody to use these kids as leverage," but called for Congress to close "loopholes" in immigration laws.

"I think what the President is saying is if the Democrats are serious, they'll come together again and try to close these loopholes and get real immigration reform," Conway said.

In an interview on CBS's "Face the Nation," Maine Republican Sen. Susan Collins called the policy "inconsistent with our American values" and reaffirmed her support for reforming immigration laws.

"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," Collins said. "That's traumatizing to the children, who are innocent victims, and it is contrary to our values in this country."

Collins and Arizona Republican Sen. Jeff Flake announced Sunday that they have sent a letter to the departments of Homeland Security and Health and Human Services about "the safety and security of young children immigrating to the United States."

The letter cites reports about a Honduran mother who sought asylum by presenting herself to authorities at an international bridge in Brownsville, Texas, and was separated from her 18-month-old child for months, as well as a similar case in Southern California.

"These accounts and others like them concern use," they wrote.

The senators requested that the departments explain how and why family separations are occurring, if there are procedures in place to keep parents informed about their children, and if the personnel who handle the children have training to make "the separation process less traumatic."

Later Sunday, Homeland Security Secretary Kirstjen Nielsen posted a statement on Twitter focusing on asylum seekers and denying any policy of separating families at the border.

"This misreporting by Members, press & advocacy groups must stop. It is irresponsible and unproductive," Nielsen wrote. "As I have said many times before, if you are seeking asylum for your family, there is no reason to break the law and illegally cross between ports of entry."

"You are not breaking the law by seeking asylum at a port of entry," she continued.

"For those seeking asylum at ports of entry, we have continued the policy from previous Administrations and will only separate if the child is in danger, there is no custodial relationship between 'family' members, or if the adult has broken a law," Nielsen added.