The surviving suspect in the Boston Marathon bombing told the FBI he and his brother initially considered committing suicide bombings and planned attacking on the Fourth of July at Boston’s large celebration along the Charles River, according to two law enforcement officials.

Dzhokhar Tsarnaev, 19, said that he and his brother, Tamerlan, 26, decided to launch their attack earlier because they completed building the pressure-cooker bombs more quickly than they expected, according to the officials, who spoke on the condition of anonymity to discuss an ongoing investigation.

Tsarnaev said they constructed the bombs in his brother’s Cambridge, Mass., apartment and considered several targets after driving around Boston in a car. He said they ultimately decided to explode the devices near the finish line of the race on Patriots’ Day, a major holiday in Boston, according to the law enforcement officials.

Both officials expressed some skepticism about Tsarnaev’s account, saying that the complexity of the bombs made it unlikely that the brothers could have completed them as fast as he claimed.

“Maybe we will never know,” said one of the officials, who has been briefed on the interrogation. “This is the story that he is telling us.”

The elder Tsarnaev was killed in a shootout with police in Watertown, Mass., four days after the April 15 bombing, which killed three people and injured more than 260. His brother escaped but was captured hiding beneath the plastic cover of a boat in the driveway of a Watertown home later that day.

The body of Tamerlan Tsarnaev was claimed Thursday by a funeral home retained by his family, a spokesman for the chief medical examiner said.

The younger Tsarnaev suffered several gunshot wounds. He was questioned by a team of FBI agents for 16 hours after he was hospitalized. He said that he and his brother were angered by the U.S. wars in Afghanistan and Iraq but that they were not affiliated with any extremist group, according to earlier reports.

In another disclosure, the two law enforcement officials said Tsarnaev told the FBI that he and his brother were partly influenced by the online sermons of Anwar al-Awlaki, the American radical cleric who was killed in a drone strike in Yemen in September 2011. Awlaki’s influence was reported last week by the Daily Beast Web site.

Tsarnaev’s disclosures came before he was arraigned in the hospital by a federal magistrate three days after he was captured. Under a 1984 Supreme Court decision, the FBI was allowed to question Tsarnaev without notifying him of his constitutional right to remain silent. Officials have said that he has remained silent since he was arraigned and represented by lawyers.

The new details about the younger brother’s description of the events, first reported on the Web site of the New York Times on Thursday night, come as the FBI and other law enforcement agencies continue trying to determine whether the brothers acted alone. Three college friends of Dzhokhar Tsarnaev were arrested Wednesday on charges of trying to cover up his suspected role in the bombing by concealing evidence and, in one case, lying to the FBI.

U.S. authorities also have been working with their Russian counterparts to reconstruct the elder brother’s visit to strife-torn regions of southern Russian over a seven-month period in 2012. Officials have said that Tamerlan Tsarnaev became more interested in radical Islamic videos after returning from Russia last July.

Federal investigators also have focused on Katherine Russell, the American woman who married Tamerlan Tsarnaev and converted to Islam. Her parents’ home in Rhode Island, where she has been staying since the bombing, was searched by the FBI on Monday.

Julie Tate contributed to this report.