Rep. Justin Amash, a Michigan independent, said Sunday that he hasn't ruled out running for president in 2020 and said House Speaker Nancy Pelosi's stance against launching impeachment proceedings "a mistake."

Speaking with CNN's "State of the Union" after he announced in a July 4th Washington Post op-ed that he was leaving the Republican Party, Amash said he "still wouldn't rule" out a a presidential bid.

"I believe that I have to use my skills, my public influence, where it serves the country best," Amash said. "And I believe I have to defend the Constitution in whatever way works best."

But, he said, he remains "confident" about his ability to keep his congressional seat, adding that he wants to continue representing his constituents. Amash drew a Republican primary challenger shortly after he first came out in favor of starting the process of impeaching President Donald Trump in May.

"It's not something that's right on my radar right now," he said of a presidential bid.

Amash was asked about Pelosi's stance against beginning an impeachment inquiry, which he strongly disagreed with.

"From a principled moral position, she's making a mistake," Amash said. "From a strategic position, she's making a mistake. If she believes, as I do, that there is impeachable conduct in [former special counsel Robert Mueller's report], then she should say so. She should tell the American people we're going to move forward with impeachment proceedings and possibly articles of impeachment."

"When she says things like, 'Oh, I think we need to have the strongest case before we move forward,' what she's telling the American people is that she doesn't think there's a strong case," he continued. "If she doesn't think that, then she shouldn't open her mouth up in the first place and say she thinks there's impeachable conduct."

Amash added that he believes "there's a strong case" for impeaching Trump and that he believes Pelosi thinks so as well.

"And if so, she should move forward and make sure the American people know what's going on because people at home aren't reading the Mueller report," Amash said. "Most people don't have time to read a 440-page report. They expect their members of Congress to do the work for them. They want Speaker Pelosi to do the work, they want other members to do the work. And if she doesn't want to go forward, then we're going to have a big problem."

Amash estimated just roughly 15 percent of congressional Republicans have read Mueller's more than 440-page report on Russian interference, whether the Trump campaign and associates conspired with the Russians and if Trump sought to obstruct the investigation.

The first congressional Republican to conclude Trump engaged in "impeachable conduct," Amash announced he was leaving the party last week. After reading Mueller's report, Amash announced his conclusion on Trump's conduct in a widely circulated Twitter thread.

Trump responded to news of Amash leaving the party with glee, calling it "great news" for the GOP that "one of the dumbest & most disloyal men in Congress is 'quitting' the Party."

"A total loser!" Trump tweeted.

Amash, who was first elected to Congress in 2010 and helped launch the House Freedom Caucus, said on CNN of Trump's Twitter barb: "Most people understand that's not how people are supposed to talk about each other, to each other, and I think he's really identified what I talked about in my op-ed."

"He thinks people owe loyalty to him," Amash continued. "But people are elected to Congress with an oath to support and defend the Constitution, not an oath to support and defend one person, the president, who happens to be from your own party."