An iconic Philadelphia restaurant has been forced to close its doors and turn away booked parties because of the government shutdown.

City Tavern at 3rd and Walnut Streets in the Old City section of the city has been told it must close until the U.S. Congress passes a spending bill.

The restaurant, which opened for the first time in 1773 and was frequented by the nation's founding fathers, sits inside Independence National Historical Park and the building is owned by the U.S. National Parks Service.

Both have been shut down since Tuesday when the federal government began its new fiscal year without agreeing on how to fund non-essential agencies. Nearly 200 park employees were also furloughed because of the funding issue.

Since the park is closed, officials told City Tavern operator Chef Water Staib on Wednesday the restaurant had to lock up as well.

Restaurant public relations director Molly Yun said they were notified there was a possibility a closure might happen, but they were allowed to remain open during the last government shutdown 17 years ago.

"We were somewhat shocked when we received the news today that we would have to close at 3 p.m.," she said. "Unfortunately, we're going to have to stay closed until the government re-opens and our hands are tied."

Yun says the restaurant was forced to cancel booked parties, including one serving 200 visitors from Japan on Wednesday night, for at least the next four days leaving patrons "angry" and "aggravated."

Should the shutdown drag on, the restaurant stands to lose hundreds of thousands of dollars and its 80-100 member staff may need to find other work.

"Hopefully we won't have to have a Plan B, C and D over the next few days, but I'm sure we'll develop something so that we can help everyone as much as we can."

Contact Vince Lattanzio at 610.668.5532, vince.lattanzio@nbcuni.com or follow @VinceLattanzio on Twitter.