(CNN) - The battle over Trump administration security clearances is heating up.
House Oversight Committee Chairman Elijah Cummings says he will keep talking to the White House before using subpoena power. But a White House official said Wednesday they think Cummings is playing games, by demanding documents they claim he knows he is not entitled to.
Cummings meanwhile says he also wants to know more about Ivanka Trump's clearance.
Pressure is mounting on the White House to explain its security clearance process.
House Democrats want answers after sources told CNN that President Trump demanded his daughter, who serves as an adviser, be given a clearance despite objections of two top administration officials.
"We're not going to comment on security clearances. That's the policy of the White House and that continues to be the policy of the White House,” Press Secretary Sarah Huckabee Sanders said. “We're also not going to get into comments and a back and forth over things that are currently dealing with the oversight."
Ivanka told ABC News in February her father wasn’t involved.
“Absolutely not,” she said in response to a question about whether she was given special treatment in the security clearance process.
"There were anonymous leaks about there being issues, but the president had no involvement pertaining to my clearance or my husband's clearance,” she said.
Sources told CNN it's possible she didn't know.
One person familiar with her process said, "She did not seek, nor have, outside counsel involved in her process as no issues were ever raised."
The revelations about Ivanka Trump’s clearance comes days after The New York Times revealed the same thing happened with her husband, Jared Kushner.
And on Wednesday, freshman Democratic Congresswoman Rashida Tlaib announced she's taking steps to launch impeachment proceedings against Trump, even as Democratic leadership say it's too soon.
"They continue to be a group that is totally taken by the small, radical leftist fringe of their party and they're completely controlled by it,” Sanders said. “They know that's not enough to beat this president, so they're going to look for other ways to do that."