The surviving suspect, Dzhokhar Tsarnaev, initially told investigators that they planned to go to New York to party after the Boston attack, one source said. The New York police commissioner also gave this account Wednesday.
Under subsequent questioning, the officials said, Tsarnaev said that the brothers had discussed a follow-up attack on Times Square.
The officials cautioned that the idea was undeveloped. One senior official described the plan as “aspirational at most.”
Tsarnaev, wounded in a shootout with police before he was captured Friday, is in fair condition at a Boston hospital. His older brother and the second suspect, Tamerlan, was killed after the shootout.
Three people were killed and more than 200 wounded when two bombs went off near the marathon finish line April 15.
The subsequent questioning happened before Tsarnaev was read his rights, the officials said.
Times Square was the site of an attempted car bomb on May 1, 2010. The bomb never detonated. Faisal Shahzad, a Pakistani-born naturalized American citizen, confessed to that plot.
Earlier Thursday, the Tsarnaev brothers’ mother, Zubeidat Tsarnaeva, insisted from Russia that her sons were innocent.