The White House has dismissed UK concerns about the use of Prestwick Airport, in Scotland, by US planes carrying bombs to Israel.
Guided bomb units were carried on two chartered planes, it is claimed
"Apparently, the British foreign minister thinks the paperwork was not in order," said spokesman Tony Snow.
"The Department of Defense does," he added. "We'll get it straightened out."
UK Foreign Secretary Margaret Beckett protested to US Secretary of State Condoleezza Rice, claiming procedures were ignored.
Mrs Beckett said: "We have already let the United States know that this is an issue that appears to be seriously at fault, and we will be making a formal protest if it appears that that is what has happened."
Britain's Daily Telegraph newspaper reported that two chartered Airbus A310 planes with a cargo of laser-guided "smart bombs" stopped at Prestwick, 30 miles south of Glasgow in western Scotland.
The Israelis have requested the munitions to attack bunkers being used by Hezbollah militants in Lebanon.
Opposition parties reacted angrily, with Scottish National Party leader Alex Salmond claiming the UK government should decide whether to "be an aircraft carrier" for the US.
Mr Salmond said that "with an escalating Middle East conflict", it was ill-advised to send bombs "to arm one side in that conflict to the teeth".
This was especially true "at a time when hundreds of civilians, many children, United Nations observers, have already been eliminated, killed, by similar weapons", he told BBC Radio 4's Today programme.
Liberal Democrat leader Sir Menzies Campbell suggested the Americans were taking the UK for granted.
"Who knows how many of these munitions may be used to cause the kind of damage to Lebanon which the prime minister of that country described in Rome as cutting his country to pieces," he said.
According to BBC Two's Newsnight programme, the US has lodged requests to bring two more planes through the UK carrying bombs and missiles for Israel over the next fortnight.
Asked whether Britain was uncomfortable about such shipments, Mr Snow replied: "I'm not sure that's the case, because these sorts of things have happened before and probably are going to happen again.
"I would be careful not to read too much into it," he said, and promised to "find out what's going on".
A Foreign Office spokesman insisted there were "procedures in place for flights carrying arms.
"It's important that they are followed. If they are not, we will raise it with the US but we are not going to comment on US flights transiting through the UK.
"The foreign secretary has discussed this issue with Condoleezza Rice."
Gordon Corera, the BBC's security correspondent, said there was "clearly some concern within the Foreign Office".
"There's embarrassment about the fact Britain might have been used as a staging post and annoyance at the fact procedures don't appear to have been followed.
Mr Snow promised to "find out what's going on" with the flights
"'Disquiet' was the word one official used to me but for that, read real annoyance," he told the BBC's One O'Clock News.
The UK's Civil Aviation Authority said it followed a series of procedures set out by the International Civil Aviation Organisation "to facilitate the international movement of civil aircraft".
These "apply to everyone who may be involved in putting or taking dangerous goods on an aircraft", its website stated.
Countries must "hold permission to carry dangerous goods" and submit to "audit-style inspections" to "check for compliance".
If insufficient information was supplied then all available evidence would be gathered to try to inform the originating state "so that action can be taken there", it said.
A spokesman for the Civil Aviation Authority was unable to confirm whether it had been informed of the contents of the flight to which Mrs Beckett referred.
A Downing Street spokeswoman refused to comment on the matter, saying it was being dealt with by the Foreign Office.
The US State Department said it would not respond either, while Strathclyde Police insisted the matter was "for the owners of the airport and/or central government", as long as "no offence has been committed".
Prestwick has supplied logistical aid for military flights since the Second World War in "moving troops and cargo", an airport spokesperson said.
"That support involves allowing crew to rest, refuelling aircraft and providing food and water.
"The airport is obliged to allow aircraft from any CAA-registered country to land here."
Meanwhile one of Tony Blair's former foreign policy advisers has criticised the prime minister's approach to the conflict between Israel and Hezbollah.
"There are times, such as the past two weeks, when a British prime minister should have been thinking less about private influence and more about public advocacy," Sir Stephen Wall wrote in the New Statesman.
"Could the Prime Minister really not speak up for the simple proposition that the slaughter of innocent people in Lebanon, and the destruction of their country and the ruin of half a million lives, were wrong and should stop immediately?"