Commerce Secretary told CNBC on Monday that there's no level on the downside in the stock market that would alter the way President Donald Trump approaches trade.

"There's no bright line level of the stock market that's going to change policy," Ross said on "Squawk Box." "The president is trying to fix long-term problems that should have been fixed a long time ago."

U.S. stock futures were starting off the third quarter Monday morning under pressure. Concerns about import tariffs imposed and threatened by Trump were again bringing out the sellers.

The Dow Jones Industrial Average last week, for the month of June and for the year was lower as of Friday's close. However, the index was nearly three-quarters of a percent higher in the second quarter.

"There is obviously going to be some pulling and tugging as we try to deal with very serious problems," he said. "There will be some hiccups long the way."

Ross said the Trump administration would never announce a stock market level for pulling back on trade even if there was one, which he stressed there's not.

"You can't deal with day-to-day stock market fluctuations," he said, adding that policy measures need to be crafted and pursued based on what's fundamentally good for the economy.

The White House is attacking what it sees as unfair trade on a number of fronts, including tariffs on steel and aluminum imports that have been met with retaliatory measures from the European Union, Canada, Mexico and China.

But Ross said it's "premature" to say whether Trump's threatened tariffs on European auto imports would come to pass.

If those auto tariffs were imposed, the U.S. could see a new round of worth as much as $300 billion, The Financial Times reported.

Ross was also asked about an Axios report that said the administration has to allow it to unilaterally raise tariffs without congressional consent, which would be acting outside World Trade Organization rules.

The Commerce secretary didn't directly address that report, but said, "We've made no secret of our view that there are some reforms needed at the WTO."

In addition to those steel and aluminum tariffs, the administration's threatened China tariffs that were announced last month were set to go into effect on Friday. If that happens, China has promised tariffs on the U.S.

Before joining the White House, Ross made his fortune in the investment world, running W.L. Ross & Co., and buying stakes in distressed assets.