"Our country will lose tens of billions [of dollars] in gross domestic product with each passing day," Johnson told reporters.
Johnson added that he is concerned that Democrats may reject the government funding bill for the 15th time, which would cause the shutdown to enter its second month.
He warned that the shutdown is disrupting the work of critical federal agencies and leaving thousands of employees unpaid.
"Air traffic controllers and TSA [Transportation Security Administration] agents and park rangers and border patrol agents, law enforcement around the country, the stewards of our nuclear arsenal will miss their paychecks. Thousands of flights will be canceled or delayed, while our borders and national security will be directly jeopardized at a very dangerous moment in world history," Johnson said.
Johnson also stressed that millions of US families could face hardship, with nutrition and childcare programs at risk of running out of funds. The official said Supplemental Nutrition Assistance Program and WIC benefits could be depleted, and Head Start centers serving about 60,000 children nationwide might close.