Great Britain face an "incredibly tough" task to retain fourth place in the medals table in the face of competition from Australia and Germany, according to the country's Olympic chief.
Lord Moynihan, chairman of the British Olympic Association (BOA), said he did not share the confidence of those who believe Team GB will surpass the achievement in Beijing in 2008 of 19 gold medals - 47 in all - and fourth place in the table.
Funding body UK Sport are predicting more medals will be won in more sports than in Beijing, but the Olympic medal table is ranked on golds won.
The BOA chairman pointed out that in last weekend's rowing World Cup two British boats that had been viewed as contenders for Olympic gold had been beaten.
Moynihan said: "It is going to be an incredibly tough ask to match the aspiration of fourth place, exceptionally tough. You watch the Germans and the Australians.
"This is not just managing expectations. I was watching the rowers at the weekend and this is the strongest rowing squad we have ever put on the water in history and they went out there and found competing - even without the whole of the world there - was really tough.
"They know how tough it is to go and deliver gold and the same with the cyclists.
"I don't share that confidence, I think we have got a major ask to hold on to fourth place and beat Germany and Australia."
Moynihan said he was fully behind the IOC's policy of ranking the medals table on golds, and used his experience as part of the men's eight who finished second at the 1980 Moscow Games to justify that stance.
He added: "I'm absolutely supportive of using gold medals. When we went in '80 and were in the final and were just pipped by the East Germans - albeit East Germans who subsequently accepted publicly they were on drugs - we were delighted with silver but we had gone there to win.
"Any sportsman or woman goes out there to win."
Moynihan is also anticipating further appeals by athletes who have missed out Olympic selection before the final Team GB squad for London 2012 is registered on July 6.
The fact that there are many host nation places - specifically given to the hosts even if the athletes or teams have not reached the usual qualification standards - is likely to result in more appeals than usual.
"I'm sure there will be more appeals, especially where host nation places are still to be selected," said Moynihan.
"We have only selected half the team and we have got a lot of host nation places to fill, such as for volleyball and beach volleyball.
"It's mainly on host nation places because almost by definition you are into qualitative judgements to a far greater extent than you would normally be."