Ministers would only say they were prepared for all eventualities, amid growing public anger over the security fiasco.
Defence Secretary Philip Hammond also dismissed calls from Labour for personnel who have given up time off and holidays to get extra payments.
Mr Hammond denounced the plans, saying trained soldiers were not "bus drivers" –a reference to workers who will receive a £500 bonus for working during the Games.
Pressure has also continued to mount on the Home Secretary Theresa May over her department's role in supervising the contract for providing security for the Olympics.
It emerged the Home Office was warned 10 months ago there could be a problem with security, in a confidential report by HM Inspectorate of Constabulary (HMIC).
Reports at the weekend also suggest five terror suspects have been allowed into the UK despite being on Home Office watch lists. Officials blamed inexperienced border staff.
Labour's Yvette Cooper said the Home Secretary had serious questions to answer while she said the Home Office was guilty of utter incompetence.
By contrast, Culture Secretary Jeremy Hunt went out of his way to defend the company, which has said it will lose millions after failing to fulfil its contract to provide more than 10,000 security staff.
Mr Hunt dismissed the problems as a hitch and said it was completely normal for firms to fail to meet contractual commitments. He described G4S's behaviour during the scandal as honourable.
At least 17,000 personnel will now be involved in security at the Olympics, which are due to begin in less than two weeks. However, it has emerged the head of an organisation representing retired police officers was never asked to help solve the shortfall.
Clint Elliott of the National Association of Retired Police Officers said they had not been contacted despite having thousands of officers on their books.
Labour yesterday backed calls for troops drafted in to cover to be paid bonuses for their time. A range of public-sector staff will receive £500 for working during the Games.
Labour's deputy leader Harriet Harman called for the extra cash for troops to come from G4S. "It shouldn't be the taxpayer that should be paying for the bonus, which I'm sure everyone thinks they should get," she said.
Meanwhile, the Home Office confirmed ministers had received a report from HMIC last September raising a number of issues to be addressed with the Games organising committee, Locog, around security.
However, it said these had already been dealt with. "We asked HMIC to carry out a number of inspections to test that Locog security planning was on track," a spokesman said. "While an early inspection highlighted issues to be addressed, a report in February 2012 said Locog was on track to deliver the required number of security personnel."
Following the HMIC report a review of security requirements led Locog to increase the number of security guards to be supplied by G4S from 2000 to 10,400.
At the same time, value of the contract more than trebled from £86 million to £284m. G4S informed ministers just last week they would be unlikely to meet the target.
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