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The US believes that Islamist terrorists are developing bombs that could evade existing airport security checks.
While there is not thought to be any specific threat the fear is that Jihadis with Western passports and who have been trained by al-Qaeda, could enter airports armed with bombs that are almost invisible to air travel security measures.
ITV News Diplomatic Correspondent John Ray reports on the new security steps being put in place today:
By ITV News Washington Correspondent Robert Moore
I think the Americans see a perfect storm brewing in the Middle East - really a war within a war - as various Jihadi groups fight each other for relevance and supremacy.
The concern in the US for counter-terrorism groups is that either Isis or its rivals in terms of al-Qaeda affiliates might seek to gain notoriety and new followers by attacking the US home land.
I don't believe there's a specific threat the US intelligence has intercepted.
But there is alarm here that some of these groups have gained deep technical knowledge of bomb-making as well as access to European followers - those are individuals who may not need a US visa and who with relative ease could get onboard a US-bound airliner.
Richard Barrett, the former head of counter-terrorism at MI6, has told ITV News that despite today's new airport security measures, the US has a "hell of a task" keeping track of would-be terror attackers.
He said that while Britain may be considered a "softer target" for any terror group with global aspirations, the threat to the UK is not much smaller than it is to the US, and in many ways it is "easier to attack Britain".
The Foreign Office updated has its travel advice on Uganda after the authorities in Kampala warned of a possible terror threat against Entebbe Airport today.
The United States has said that it has received a "specific" threat of a terrorist attack at Entebbe International Airport in Uganda, according to an official Embassy website.
In a statement on their website, the US Embassy in Kampala has said that it has received information from the Uganda Police Force that there is a "specific threat to attack Entebbe International Airport by an unknown terrorist group today between the hours of 2100-2300."
The message goes on to warn of the continued threat of potential terrorist attacks in Uganda and urges US citizens to be vigilant.
An animation by NATS, the UK air traffic control service, maps the 2-3,000 aircraft flying across the North Atlantic every day.
The video above shows the 2,524 flights that travelled between Canada, the US and Europe on a single day in August 2013.
Security sources have told ITV News that there is "no single bit of intelligence" to prompt increased security at UK airports.
ITV News Westminster Producer Adam Smith reports:
Increased security at UK airports is not just a "blip for a week", but part of an evolving review of the UK's terror defences, the Deputy Prime Minister says.
Security is being increased in British airports after the US warned of a new bomb which could evade existing checks and scanners.
The heightened checks were not expected to cause significant disruption to passengers, the Department for Transport said.
"I don't want people to think this is a blip for a week; this is part of an evolving and constant review about whether the checks we have in airports keeps up with what we know from intelligence about the nature of the threats we face," Nick Clegg said on LBC.
"People should not be unduly panicked or concerned but this is the world we now live in. This won't be the last time that further adjustments are made because we are having to constantly evolve our own defences in view of the evolving way people want to attack us."
Nick Clegg has told Good Morning Britain it is "very important" that Britain works with the US to ensure a response to "credible" new terror threats.
Following the news that security measures at UK airports will be increased, the Deputy Prime Minister said, "We will play our part, as will other countries, to make sure that where security checks can be tightened up, they will be tightened up."
Asked if there was an increased terror threat, Mr Clegg said: "There's always a shifting contest if you like where people who want to do us harm are trying to find new ways of doing so.
"We need to anticipate that and ... try and deal with the new ways in which they are trying to do us harm."
Latest ITV News reports
Manchester Airport promised that passenger delays today caused by new air travel security measures were simply a "teething problem".