By David Lawder

WASHINGTON (Reuters) - U.S. Treasury Secretary Steven Mnuchin said on Friday that he believes financial markets could improve "significantly" once they fully reflect the potential for U.S. economic growth from President Donald Trump's economic policies.

Mnuchin said at an event sponsored by news website Axios that optimism about U.S. growth from policies such as regulatory reform and tax reform is "definitely not all baked in" to market valuations.

U.S. stock prices and the dollar have strengthened significantly since Trump was elected in November, largely in anticipation of corporate profits rising as regulatory burdens ease and tax rates fall. Some of those gains were retraced this week as Republicans in Congress faced stiff opposition from conservatives in passing a bill to replace the Obamacare health law.

"I think there is some good news that's baked in, but yet, I think there is further room for significant growth in the economy that would be reflected in the markets," Mnuchin said.

"The consequence would be that the market could go up significantly," Mnuchin added.

Treasury secretaries in the past have shied away from publicly discussing market valuations.

But Mnuchin said Trump's policies could produce growth of 3 percent to 3.5 percent, which is significantly higher than the fourth quarter reading of 1.9 percent.

"We're in an environment where the U.S. assets are the most attractive assets to invest in on a global basis."

Mnuchin said he is still aiming to achieve passage of comprehensive tax reform by the time Congress takes its August recess. He also said he expects the Trump administration's Obamacare replacement bill to pass later on Friday.

(Reporting by David Lawder; Editing by Jeffrey Benkoe and Chizu Nomiyama)