Earlier Thursday, his campaign said in a fact sheet that its planned tax cuts and deregulation will boost average annual GDP growth to 3.5 percent and "create as many as 25 million new jobs" in the next decade. The U.S. economy grew at roughly 2 percent in 2015 and last grew at a 4 percent annual rate in 2000.

"My great economists don't want me to say this, but I think we can do better than that," he said Thursday in a speech to the Economic Club of New York.

Donald Trump thinks American GDP can grow more than 4 percent under his policies, more than double the average rate the U.S. has seen in this century.

Republican presidential nominee Donald Trump speaks at an event hosted by The Economic Club of New York at the Waldorf Astoria hotel in New York on September 15, 2016.

The fact sheet cited "Trump economists" without independent backing. Independent analyses have often proven skeptical of the Trump campaign's estimates.

Trump, speaking later in a restrained tone by his standards, started his speech by boasting about his gains in polls against Democrat Hillary Clinton. He then tried to contrast his plans from Clinton's, claiming she would stifle the economy with regulation and tax increases on the wealthy.

"My plan will embrace the truth that people will flourish under a minimum government burden," Trump said.

Trump contended his 4 percent growth goal will "reduce the deficit." Previous independent analyses of his broad tax cuts have estimated they will bloat the U.S. deficit by trillions, even after economic growth is taken into account.

He has proposed three income tax brackets of 33 percent, 25 percent and 12 percent, down from seven brackets and a top rate of nearly 40 percent currently. Trump also wants to cut the corporate tax rate to 15 percent from about 35 percent now.

Trump also renewed his call for a moratorium on federal regulations, saying he will scale back "years of disastrous regulation." He once again called to eliminate the Environmental Protection Agency's Clean Power Plan, which aims to reduce carbon emissions from coal-fired power plants, among other regulations.

He also took shots at some of his favorite targets of the campaign trail, criticizing China as a currency manipulator and pledging to renegotiate the North American Free Trade Agreement and pull out of the Trans-Pacific Partnership.

Trump again bashed Ford's recent decision to move its small-car production to Mexico.

— CNBC's Gina Francolla contributed to this report.