One of President-elect Trump's top advisers said Tuesday that pieces of a replacement for the Affordable Care Act have already been conceived, but said a full replacement isn't ready.

Kellyanne Conway, incoming White House counselor to Trump, said on MSNBC that ideally a replacement for Obamacare would be put in place right after it's repealed. However, she said that might not be practically possible.

"We have pieces of it," she said. "But, we don't have a (Department of Health and Human Service) secretary confirmed yet."

She added that Democrats would need to chip in by working with Republicans on a replacement for Obamacare. "We're ready to go but we're not the only party," she said.

Repealing Obamacare is the number one priority for Trump and Republican lawmakers once Trump is sworn into office on Jan. 20. Conway indicated, however, that it might take years to finally eliminate and replace what is arguably President Obama's most significant achievement.

"That's the ideal situation," she said of putting a replacement in immediately. "Let's see what happens practically. Some people, some experts say it could take years to complete the process."

She said it's clear that ensuring people with pre-existing conditions have coverage is popular, and would likely be in a future replacement bill. She also reiterated Trump's promise to not take away healthcare coverage from people who received it while Obamacare was in place.

"We don't want anyone who currently has insurance to not have insurance," she said. "We're very aware the public likes coverage for pre-existing conditions."