The US Senate blocked bipartisan legislation yesterday aimed at tightening restrictions on the sale of firearms.

It was a huge defeat for President Barack Obama and a rejection of personal pleas by families of the victims of last winter's mass school shooting in Connecticut.

An attempt to ban assault-style and a ban on high-capacity ammunition magazines were also rejected in series of showdown votes four months after a gunman killed 20 school children and six staff members at Sandy Hook Elementary School.

Among those who died was six-year-old Dylan Hockley whose family had moved to the US from Hursley in Hampshire.

The background check measure commanded a majority of senators, 54-46, but that was short of the 60 votes needed, as 41 Republicans and five Democrats joined together to sink the plan.

Speaking to the nation after the vote Mr Obama said a minority the senators decided ''it wasn't worth it'' to protect the nation's children.

''All in all, this was a pretty shameful day for Washington,'' he said.

The vote was also jarring blow to the drive to curb firearms sparked by December's massacre of 26 young children and staff at an elementary school in Newtown, Connecticut.

The president has made it a priority on his domestic agenda in the months since the massacre, making several trips outside Washington to try to build support.

Last week, he travelled to Connecticut, and he invited several parents to fly back to Washington with him on board Air Force One so they could personally lobby lawmakers.

Some of the parents of the Sandy Hook victims watched the votes from the spectators' gallery that rings the Senate floor. They were joined by relatives of victims of other mass shootings in Arizona, Virginia and Colorado.

The roll call was a victory for the nation's most powerful gun lobby, the National Rifle Association, which opposed the plan as an ineffective infringement on gun rights.

The proposal would have required background checks for all transactions at gun shows and online. Currently they must occur for sales handled by licensed gun dealers.

Even before the vote began it was apparent that the bill was in deep trouble with a growing number of senators saying they would vote against the measure.

In the hours before the key vote, Senator Joe Manchin, one of the bill's sponsors, bluntly accused the NRA of making false claims about the expansion of background checks.

''I don't know how to put the words any plainer than this: That is a lie. That is simply a lie,'' he said, accusing the organisation of telling its supporters that friends, neighbours and some family members would need federal permission to transfer ownership of firearms to one another.

The NRA did not respond immediately to the charge, but issued a statement after the vote that restated the claim.

The proposal ''would have criminalised certain private transfers of firearms between honest citizens, requiring lifelong friends, neighbours and some family members to get federal government permission to exercise a fundamental right or face prosecution,'' said a statement from Chris Cox, a lobbyist for the group.

The votes, however, were unlikely to be the last word on an issue that Democratic leaders shied away from for nearly two decades until Mr Obama picked up on it after the Newtown shootings.

''This effort isn't over,'' the president vowed at the White House moments after the defeat. Surrounded by Newtown relatives, he said opponents of the legislation ''caved to the pressure'' of special interests in casting their vote.

The bipartisan approach was widely seen as the best chance for winning enough Republican votes to change current law in a way that Mr Obama and gun control groups support.

But opponents had proposals of their own, including one that would require states that issue concealed weapons permits to honour the permits from other states.

Numerous polls in recent months have shown support for enhanced gun control measures, including background checks, though it may be weakening.