It comes as Destination DC, the capital’s tourist board, reinforced the message to TTG that “DC is open for business” and budget-conscious travellers could take advantage of various discounts to visit the US capital in its off-peak season. It has created a dedicated hashtag and landing page on the website called #DCIsOpen.

The shutdown – now the longest in US history – has entered its fifth week as president Donald Trump continues to reject any spending bills that don’t include $5.7 billion to build a wall along the US-Mexico border.

The impasse has left thousands of government workers without pay including airport security staff and caused major attractions to close, including museums and national parks.

But agents and operators have reported strong US sales.

Andrew Earle, managing director of Andrew Earle’s Holidays, said the shutdown was not having any impact on bookings to the US, with New York and multi-centres combining Las Vegas, San Francisco and Los Angeles proving popular, helped by cheap flights across the Atlantic.

He added: “Our numbers to the US are holding up, with the majority of bookings for travel beyond June. We’re not seeing much in terms of lates, but that’s not entirely unusual.

“We’ve not seen as much touring come in during January as normal, so it may be that the 60-plus market is a bit more anxious and holding back. We are already being asked for 2020.”

But Earle said that the US shutdown was “starting to create questions from customers”.

“If it’s still going on in another 12 weeks with Easter coming up then it will become more of an issue,” he added. “People paying their balances who are travelling in April to national parks are asking questions.”

Richard Dixon, director of Holidaysplease, said: “The US continues to be strong for us – we’re seeing some great prices to New York with really attractive deals. Cheap airline seats in the market are encouraging people to go out there.”

Dixon agreed that because of the time of year, the shutdown was not having an effect on bookings so far.

“If it continues into spring and then summer, then it could cause a major problem for people going to the national parks,” he added.

Premier Holidays said the US had been “selling exceptionally well” compared to this time last year, and is currently 30% up year-on-year for travel in 2019. Similarly, Travel 2 has seen a 25% increase in sales to the US over the past three months, with Florida leading the way.

Destination DC president and chief executive Elliott Ferguson told TTG: “There’s a perception that all is shut down, but this isn’t the case.”

While the 19 Smithsonian museums are closed due to their affiliation with the federal government, Ferguson said there are “a series of amazing museums open”. Sites including the Lincoln Memorial and the National Mall also remain open.

Ferguson recommended clients planning a trip visit Washington.org for discounts and itinerary ideas.