WASHINGTON • By all accounts, Saturday was a near-perfect day to be a tourist in Washington.

It was unseasonably warm, and the sun cast a soft orange glow on the monuments and cupola, creating the postcard-like scene that draws so many visitors to the city.

Legions of strollers took to the winding paths of the National Zoo, where a tiger's deep bellow rang out over the chatter of visitors.

But the partial government shutdown cast a shadow on the day.

So far, the Smithsonian Institution's museums, research centre and zoo have been spared from the shutdown that has furloughed thousands of federal employees.

But if the closure continues beyond New Year's Day, all Smithsonian institutions will shutter, locking visitors out of tourism mainstays like the National Zoo, the National Museum of American History and the National Museum of African American History and Culture. The National Gallery of Art Sculpture Garden ice rink will also close.

"We have no control over this," said Ms Linda St Thomas, spokesman for the Smithsonian Institution. She lamented that closures were bound to disappoint visitors next week, many of whom make visiting the free museums a central part of their trips to the nation's capital. Tourists often have their heart set on seeing the 45-carat Hope Diamond at the National Museum of Natural History, or the portraits of the Obamas at the National Portrait Gallery.

"The Smithsonian museums are a big part of a person's trip to Washington," Ms St Thomas said.

The partial shutdown is set to be one of the longest in history, the result of an impasse between President Donald Trump, who is demanding billions for a border wall, and congressional Democrats, who refuse to authorise the funding.

There were few signs that the shutdown would end any time soon, with Mr Trump tweeting threats to close the entire southern border if he did not get funding for the wall. Lawmakers are not scheduled to return until at least Jan 2.

The shutdown has meant about 800,000 federal workers are without pay cheques during the holiday season, plunging many low-wage workers into economic peril.

Ms Lucy Asmat, 53, a nurse visiting from Lima, Peru, said that the attractions "are not just for Americans". "They are for foreigners, like us, who want to see all the beautiful things that you have in the United States. The wall should not be a priority."

But Mr Ralph Pariente Jr, from Miami, backs Mr Trump and believes the border wall is necessary."I feel bad for the employees who aren't getting paid... but nothing ever gets done."