Mark Barden, whose son Daniel was among those killed in the Newtown massacre, has said families of the victims are heartbroken at the Senate's blocking of gun ownership legislation but will continue to campaign for stronger weapon controls.
He issued an emotional plea at the White House after a plan aimed at expanding background checks for gun buyers failed to receive enough support in a vote.
With President Obama looking on, Mr Barden said: "We always knew this would be a long road. We don't have the luxury of turning back."
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A colder start to the day with outbreaks of rain expected across Wales and southern England.
A further 85 buses are expected to arrive on Tuesday and Wednesday, with officials saying the entire operation will last at least a week.
The reality star had filed a defamation lawsuit against celebrity gossip site MediaTakeOut.com.