The Boston Marathon bombers considered suicide bombings and launching an attack on July 4 – American Independence Day – the surviving suspect reportedly told interrogators.
Dzhokhar Tsarnaev told authorities that he and his elder brother, Tamerlan, brought the bombing forward to April after finishing their pressure-cooker bombs faster than expected.
The 19-year-old, who is recovering in hospital from multiple gunshot wounds, reportedly said the bombs were built in a small flat which he shared with his brother and Katherine Russell, Tamerlan's wife, and their baby daughter.
The claim will raise fresh questions about whether Ms Russell (24) had any prior knowledge of the attack and when she realised her husband was responsible. She insists she knew nothing of her husband's actions.
Investigators are increasingly focused on whether Tamerlan, who died in a shootout with police, received terrorist training outside the US.
"The belief – with no actual proof yet – is that they were trained somewhere, probably in Chechnya or Pakistan," Peter King, chairman of the House sub-committee on counter-terrorism, said.
Tamerlan's body was finally collected by family members late on Thursday night, two weeks after his death in Watertown, outside Boston.
The family has not announced plans for a funeral service and a mosque that Tamerlan infrequently attended has refused to perform a service. (© Daily Telegraph, London