LONDON — More than 600,000 vacationers who booked through tour operator Thomas Cook were on edge Sunday, wondering if they will be able to get home, as one of the world's oldest and biggest travel companies teetered on the edge of collapse.

The debt-laden company, which confirmed Friday it was seeking 200 million pounds ($250 million) in funding to avoid going bust, was in talks with shareholders and creditors to stave off failure.

A collapse could leave around 150,000 travelers from Britain stranded, along with hundreds of thousands from other countries. The company has sought to reassure customers that flights were continuing to operate as normal.

Most of Thomas Cook's British customers are protected by the government-run travel insurance program, which makes sure vacationers can get home if a British-based tour operator goes under while they are abroad.

Thomas Cook's financial difficulties also raised questions about the jobs of the 22,000 people employed by the company around the world, including 9,000 in Britain.

Unions and Britain's opposition Labour Party urged the government to intervene financially to save jobs if the company fails to raise the necessary financing from the private sector.

If the company collapsed, Britain's Civil Aviation Authority would probably be ordered by the government to launch a major operation to fly stranded vacationers home, much as it did when Monarch Airlines went bust nearly two years ago.

British Foreign Secretary Dominic Raab gave assurances that British vacationers will not be left stranded.

"I don't want to give all the details of it because it depends on the nature of how people are out there," he told the BBC. "But I can reassure people that, in the worst-case scenario, the contingency planning is there to avoid people being stranded."

Rebecca Long Bailey, Labour's business spokesperson, said the government "faces a simple choice between a 200 million-pound government cash injection to save the company now versus a 600 million-pound bill to repatriate U.K. holidaymakers."

Thomas Cook, which began in 1841 with a one-day train excursion in England and now operates in 16 countries, has been struggling over the past few years. It only recently raised 900 million pounds ($1.12 billion), including from leading Chinese shareholder Fosun.

In May, the company reported a debt burden of 1.25 billion pounds and cautioned that political uncertainty related to Britain's departure from the European Union had hurt demand for summer holiday travel. Heat waves over the past couple of summers in Europe have also led many people to stay at home, while higher fuel and hotel costs have weighed on the travel business.

The company's troubles appear to be already affecting those traveling under the Thomas Cook banner.

A British vacationer told BBC radio on Sunday that the Les Orangers beach resort in the Tunisian town of Hammamet, near Tunis, demanded that guests who were about to leave pay extra money for fear it wouldn't be paid what it is owed by Thomas Cook.

Ryan Farmer, of Leicestershire, said many tourists refused the demand, since they had already paid Thomas Cook, so security guards shut the hotel's gates and "were not allowing anyone to leave."

It was like "being held hostage," said Farmer, who is due to leave Tuesday. He said he would also refuse to pay if the hotel asked him.

The Associated Press called the hotel, as well as the British Embassy in Tunis, but no officials or managers were available for comment.