Mr Trump also told Fox News the Chinese had lived too well for too long.
The US and China have slapped tit-for-tat tariffs on hundreds of billions of dollars of each other's goods over the past few months.
Investor worries about the escalating trade conflict have rattled financial markets.
In a telephone interview on the Fox & Friends programme on Thursday morning, Mr Trump said his trade policies had inflicted economic pain on China.
"I put $250bn worth of taxes, or tariffs, on China and it's had a big impact. If you look at their economy now it's a whole different ball game.
"Their economy has gone down very substantially. And I have a lot more to do if I want to do it and I don't want to do but they have to come to the table.
"They want to negotiate, they want to negotiate badly, but I told them, 'You're not ready yet. You're not ready yet.'
"They lived too well for too long and frankly I guess they think that the Americans are stupid people. Americans are not stupid people."
Mr Trump also renewed his criticism of the US central bank.
He said the Federal Reserve was being "too aggressive" by raising interest rates this year and getting "a little bit too cute".
The Republican president told the presenters: "They're [Fed bankers are] making a big mistake."
His comments followed several days of declines in US stock markets.
White House officials have dismissed the declines as standard corrections after a streak of higher prices.
But a fall would be a concern to the president, who frequently cites stock market performance as a sign of his administration's success.
Hundreds of companies are due to provide investors with updated earnings forecasts in coming weeks.
Analysts say some of the recent share price declines may be due to sales by investors worried that trade tensions will hurt growth, while trade tariffs and rising interest rates raise costs for businesses.
By historic standards, interest rates remain low.
But the Federal Reserve has been gradually raising its interest rates since 2015, bringing the target for its benchmark rate to a range of 2% to 2.25% last month.
The Fed has said strong economic performance in the US means the the ultra-low levels put in place to spur economic activity after the 2008 financial crisis are no longer necessary.