London: The struggling Caterham and Marussia Formula One teams will both miss next week`s U.S. Grand Prix in Austin, Texas, the sport`s commercial supremo Bernie Ecclestone told Reuters on Saturday.
"Neither of those two teams are going to go to America," said the 83-year-old.
Their absence will increase concern in the sport, whose smaller outfits have been saying for some time that they risk going out of business unless costs are slashed, even though Ecclestone has said he would be happy with 10 teams.
Caterham went into administration on Friday while Russian-registered Marussia are also struggling financially and are still reeling from French driver Jules Bianchi`s serious accident in Japan three weeks ago.
The air transport for all the teams` cars and freight is organised by Ecclestone`s Formula One Management and they were due to be flown out on Saturday.
Representatives of Marussia, who are currently ninth in the championship thanks to Bianchi`s ninth place in Monaco in May, were not immediately contactable.
However Caterham`s administrator Finbarr O`Connell told Sky Sports television that the cars remained in the factory at Leafield.
"The racing kit was heading towards Austin but it`s still in the UK. It will stay in the UK and hopefully if Caterham races in one of the last races we will ship the racing kit from here," he said.
O`Connell added that there had been "10 to 15 serious interested parties on the phone today and we are speaking to all those and getting information together for them to examine."
By missing the race in Austin, the two teams will also be absent from Brazil since the races are back to back with the cars going direct from the United States to Brazil before returning to Europe.
The 19th and final race of the season is in Abu Dhabi on Nov. 23, when double points are to be awarded for the first time.
Ecclestone said on Friday that Caterham had been given a dispensation to miss the next two races while they sought a buyer.
Marussia`s absence, apart from giving 10th placed Sauber more of chance to overtake them in the championship, will leave the grid in Austin with only nine teams and none of the three entirely new entrants that made debuts in 2010.
Of that trio, HRT folded at the end of 2012.
The 18-car grid will be the smallest since Monaco in 2005, when the BAR team were banned for two races for a breach of the technical regulations.
The absence of Marussia also wrecks the hopes of American Alexander Rossi, the reserve driver, making a home appearance at Austin although the team had yet to make any announcement about their line-up.
Rossi almost stepped in at the Belgian Grand Prix for Britain`s Max Chilton when contractual problems emerged.
At the time, Chilton`s management suggested he had voluntarily stepped aside "to allow the team to attract much-needed funds by selling his seat" and Marussia were in talks with new investors.
Reports in the European media have indicated that Russian majority owner Andrei Cheglakov has been looking to sell for some time.
Ferrari-powered Marussia ran only one car in Sochi, Russia, two weeks ago, as a mark of respect for Bianchi who remains in critical condition in hospital in Japan after his horrific crash at Suzuka.
There has been no medical update on Bianchi`s condition since Sochi.
Caterham`s two drivers are Japan`s Kamui Kobayashi and Sweden`s Marcus Ericsson.