HONG KONG — China’s companies racked up some towering bills as they expanded, and the world’s investors and lenders rushed to offer them even more money.

Now the bills are coming due, and a growing number of Chinese companies can’t pay up, in a sign that the world’s No. 2 economy is feeling the stress from its worst slowdown in nearly three decades.

Two high-profile companies — a giant government-run trading firm and a conglomerate backed by China’s most distinguished university — are the latest to join a long list of Chinese businesses that have run short of cash when it was time to pay back their debts. Chinese corporate borrowers have defaulted on nearly $20 billion in loans this year.

The amount is small compared with China’s overall economy, but the toll is rising. Chinese companies owe hundreds of billions of dollars in debt that is coming due over the next two years, including more than $200 billion owed to lenders and investors around the globe.