Vehicle certification is among the functions halted by the nearly four-week partial shutdown of the federal government, meaning automakers could face delays in launching new and updated models if the impasse in Washington drags on.

Under the Clean Air Act, new vehicles and engines can't be sold legally in the U.S. without approval from the EPA. Jim Farley, Ford Motor Co.'s president of global markets, noted this week that the automaker has a number of important products headed to dealerships this year, including the redesigned Explorer and Escape, as well as the new Lincoln Aviator.

"We're all waiting in lines," Farley said at the Automotive News World Congress in Detroit. "Every new vehicle has to get certified through the government. If that gets backed up, so do the launches."

Farley said Ford doesn't have any vehicles scheduled to launch in the next few months, though.

"Thankfully, ours are positioned more in the spring and summer," he said. "I don't know what's going to happen. If this continues ... who knows?"

General Motors on Wednesday confirmed it is "among the automakers that are awaiting decisions in the certification process." Pat Morrissey, a spokesman for the company, declined to comment on how many 2020 model-year vehicles are caught in the certification process.

GM North America President Alan Batey on Monday told Automotive News that the company's business operations had not been impacted by the government shutdown.

Morrissey said the automaker waiting on EPA certification doesn't necessarily mean it's impacting GM's operations at this point.