Marathon bombers planned to carry on and attack New York

Police commissioner Raymond Kelly told a briefing that the two suspects had a pressure cooker bomb and five pipe bombs they wanted to set off.

They said Dzhokhar Tsarnaev told Boston investigators from his hospital bed that he and his brother had discussed going to New York to detonate their remaining explosives. They decided it spontaneously.

Tsarnaev travelled to New York at least once last autumn. There is a photo of the suspect in Times Square.

The plan fell apart after the Tsarnaev brothers were intercepted by police in a stolen car and got into a fierce gun battle that left Tamerlan Tsarnaev dead, Mr Kelly said.

Dzhokhar, 19, is charged with carrying out the April 15 bombing that killed three people and wounded more than 260, and he could get the death penalty.

He was interrogated in his hospital room over a period of 16 hours without being read his constitutional rights. He immediately stopped talking after a magistrate judge and a representative from the US Attorney’s office entered and read him his rights, according to a US law enforcement official.

The developments in New York came as US officials told the Associated Press that the federal government added Tamerlan’s name to a terrorist database 18 months before the attacks.

Dzhokhar Tsarnaev told authorities that his older brother only recently recruited him to be part of the attack, two US officials said yesterday.

The CIA, however, named Tamerlan, 26, to a huge, classified database of known and suspected terrorists 18 months ago, officials said, an acknowledgment that will undoubtedly prompt congressional inquiry about whether the Obama administration adequately investigated tips from Russia that Tsarnaev had posed a security threat.

Shortly after the bombings, US officials said the intelligence community had no information about threats to the marathon.

Investigators have said the brothers, Russian-born ethnic Chechens, appeared to have been radicalised through jihadist materials on the internet and have found no evidence tying them to a terrorist group. Tamerlan, whom authorities have described as the driving force behind the plot, was killed in a shootout with police. Dzhokhar is recovering in hospital from injuries sustained during a getaway attempt.

The CIA made the request to add Tamerlan to the database after the Russian government contacted the agency with concerns he had become a follower of radical Islam.