Mr Raab told the BBC’s Andrew Marr Show contingency planning was in place to make sure no-one would be stranded.
But he dampened hopes of a government rescue bid for the firm.
Ministers did not “systematically step in” when businesses went under unless there was “a good strategic national interest”, he said.
Mr Raab said he did not want to undermine the rescue talks that Thomas Cook is currently conducting with its biggest shareholder and creditors in the City of London.
The tour operator’s financial difficulties have mounted over the past year, culminating in a refinancing plan in August led by its biggest shareholder, Chinese company Fosun.
But banks now want the company to raise extra funds and it could fall into administration within days unless it finds £200m.
The Civil Aviation Authority (CAA) has aircraft on standby in case Thomas Cook does go into administration over night.
The BBC understands that those aircraft are currently being flown to destinations so that British tourists can be flown home on Monday if necessary.
A source said the CAA is “very prepared”.
The Transport Salaried Staffs Association (TSSA) union, which represents Thomas Cook staff, is urging the government to step in with a bail out amid fears the company’s collapse could leave about 150,000 British tourists stranded.
Thomas Cook customers have been reminded on social media that they have Atol protection – a fund paid for through industry levies – “in the event that Thomas Cook goes into administration”.
The travel firm also reassured customers on Sunday that flights continue to operate as normal.
Katie Prescott, business correspondent
This meeting is crucial for Thomas Cook’s survival.
If there is no agreement, then the decision to wind up the company will be taken at a board meeting this evening. It’s likely (looking at the precedent of Monarch’s collapse) that any announcement about that will be made late at night, once all planes are on the ground. But the company doesn’t have to announce anything until the markets open at 07:00 BST on Monday.
It’s low season at the moment, the time of year when Thomas Cook has to pay its suppliers for the busy summer season just gone. Hoteliers are paid on 60 to 90-day terms, once travellers have already taken their holidays. The nightmare scenario is that hoteliers who don’t think they will get paid might turn out the people staying with them.
However, it is worth re-stating that the company is still trading. People are still holidaying with Thomas Cook. And while we can assume the company is reining back marketing activity around last-minute deals and offers, until any announcement is made, it is business as usual.
The foreign secretary said he did not want talk of contingency planning to become “a self-fulfilling prophecy”.
He told the BBC the government had learned lessons from the collapse of the Monarch airline in 2017. The UK’s consular authorities abroad were ready to assist, he said.
A government spokesperson described the situation as a “worrying time for holidaymakers and employees”.
They added: “The financial circumstances of individual businesses are a commercial matter, but the government and the Civil Aviation Authority are monitoring the situation closely.”
The view from Majorca
By BBC Europe reporter Gavin Lee
As Thomas Cook customers anxiously wait to see if and how their holidays might be affected, some say they have already found themselves in “horrible” situations abroad.
Customers at a hotel in Tunisia say they were prevented from leaving the property on Saturday unless they paid extra fees – thousands of pounds in some cases – to cover what the resort says it is owed by the tour operator.
In Majorca, it’s a different story.
Liz Preston said there were cheers when her plane took off from Gatwick.
“It was a moment that captured the sheer relief really, that we could still have a holiday, as well as the fact that it might be one of the last ever flights,” she said.
The Thomas Cook staff were in reassurance mode, urging customers to enjoy their holiday, but advising them to keep an eye on the news if the situation changes and their return flight becomes difficult.
Richard Stevens from Faversham in Kent said he’s “gutted” Thomas Cook is in such trouble, because he’s been coming on Thomas Cook package holidays with his wife and two sons for “donkey’s years”.
The domino effect of Thomas Cook’s collapse on this holiday island would be significant.
Hundreds of smaller industries rely on the through-flow of Thomas Cook travellers for excursion tours, water sports, as well as cafes and bars.
Caledonia Tours is a company that offers sightseeing trips. Tour operator Lucas Pantone says 80% of his business is from Thomas Cook. “If it goes under” he says, “we’ll be having a crisis meeting within hours, over whether we can survive”.
There are currently 600,000 Thomas Cook customers on holiday, of which 150,000 to 160,000 are British.
One of the world’s largest travel companies, Thomas Cook was founded in 1841 to operate temperance day trips, and now has annual sales of £9bn.
It employs 22,000 staff, 9,000 of whom are in the UK, and serves 19 million customers a year in 16 different countries.
In July, Thomas Cook produced a business plan saying that it needed £900m in refinancing, up from a previous estimate of £150m. The £900m would come from China’s Fosun, the group of creditors and some other investors.
The group of lenders then commissioned an independent investigation. Its financial advisers said Thomas Cook would require an additional £200m on top of the £900m already required, which would bring the total refinancing needed up to £1.1bn.
Thomas Cook succeeded in finding a backer to provide the additional £200m, but the BBC understands it has since pulled out.
The firm has blamed a series of problems for its profit warnings, including political unrest in holiday destinations such as Turkey, last summer’s prolonged heatwave and customers delaying booking holidays because of Brexit.
Brian Strutton, the general secretary of the British Airline Pilots Association, said: “Ministers need to step forward and take responsibility for the sake of passengers and staff.
“There is a real risk that if the worst comes to the worst proper arrangements may not be in place for the repatriation programme and staff are still working while not knowing if they have a job or will even get paid for this month.”
Shadow business secretary Rebecca Long Bailey said “the government must consider stepping in and taking an equity stake to avoid this crisis”.
What are your rights?
If you are on a package holiday you are covered by the Air Travel Organiser’s Licence scheme (Atol).
The scheme will pay for your accommodation abroad, although you may have to move to a different hotel or apartment.
Atol will also pay to have you brought home if the airline is no longer operating.
If you have holiday booked in the future you will also be refunded by the scheme.
If you have booked a flight-only deal you will need to apply to your travel insurance company or credit card and debit card provider to seek a refund.
When Monarch Airlines collapsed in 2017, the government organised to bring home all the stranded passengers, whether they were covered by Atol or not.