Washington (AFP) - Air travel in the United States could soon “slow to a trickle,” authorities warned Sunday as thousands more flights were cancelled or delayed and passengers faced chaos triggered by the federal government shutdown.

Transportation Secretary Sean Duffy said the number of flights being snarled or cut would multiply if the funding impasse between Democrats and Republicans continues while Americans gear up to travel for the Thanksgiving holiday later this month.

“It’s only going to get worse,” Duffy said on CNN’s “State of the Union,” a Sunday news talk show. “The two weeks before Thanksgiving, you’re going to see air travel be reduced to a trickle.”

Meanwhile, the Senate took the rare step of meeting Sunday to convene a test-vote on ending the shutdown, which has stretched to a record 40 days.

Senate Majority Leader John Thune, a Republican, told reporters Sunday that a potential deal was “coming together,” in the latest sign of activity on Capitol Hill that could see a reopening of government on the horizon.

US media reported the potential deal would be a budget package that includes short-term government funding through January.

By Sunday evening the number of cancellations of flights within the United States and to and from the US had surpassed 2,300, with more than 8,000 delays, according to data from tracking platform FlightAware.

Airports that were particularly hard hit included the three New York City area airports, Chicago’s O’Hare, and Hartsfield-Jackson in Atlanta.

Newark’s Liberty International Airport – a major northeastern US hub – was among the worst-hit. Twenty-seven percent of flights due to leave Newark were scrapped, with delays to 40 percent of outbound flights, FlightAware showed.

At New York’s LaGuardia Airport more than half of all outbound flights were delayed.

Duffy warned that many Americans planning to travel for the November 27 Thanksgiving holiday “are not going to be able to get on an airplane, because there are not going to be that many flights that fly if this thing doesn’t open back up.”

The Thanksgiving weekend also kicks off the busy winter shopping season on which many retailers rely.

- ‘People are hurting’ -

Travelers expressed their frustration on social media. “Moral of the story, if you don’t have to travel and have a low patience threshold, don’t fly,” said one.

Sunday marked the third day of flight reductions at airports nationwide, after the Trump administration ordered reductions to ease strain on air traffic controllers working without pay.

“We’re going to see air traffic controllers, very few of them coming to work, which means you’ll have a few flights taking off and landing,” Duffy told Fox News Sunday.

Duffy sought to blame Democrats for the high-stakes political standoff, but Senator Adam Schiff said Republicans were rejecting a “reasonable” compromise deal to end the shutdown.

“And the result from the Senate Republicans was ‘no,’ from the House Republicans ‘we are staying on vacation,’ and from the president ‘I’m going out to play golf,’ and that’s where we are while people are hurting,” Schiff said.

When asked whether Democrats would turn around and vote with Republicans, Schiff, a California Democrat, indicated that the issue of healthcare subsidies remained a sticking point in negotiations.

Democrats to date have refused to vote for re-opening the government unless the subsidies for the Affordable Care Act, also known as Obamacare, are extended as part of the deal. They are set to expire at the end of this year.

“Let’s just extend the ACA for a year, reopen the government, and then we can negotiate a more permanent fix to this crisis in health care in this country,” Schiff said on ABC’s “This Week with George Stephanopoulos.”

“We need to end this. We proposed something, I think very reasonable. It was a compromise. Certainly wasn’t everything I want, which is a permanent extension of the tax credits,” he said, urging Republicans to allow “more time to work on this and reopen the government.”