He’s still in serious condition and unable to speak, but Boston bombing suspect Dzhokhar Tsarnaev is providing investigators with a wealth of information about the plot already.

The 19-year-old suspect in the Boston Marathon bombings has told interrogators that the American wars in Iraq and Afghanistan motivated him and his brother to carry out the attack, according to U.S. officials familiar with the interviews.

From his hospital bed, Dzhokhar Tsarnaev has acknowledged his role in planting the explosives near the marathon finish line on April 15, the officials said. The first successful large-scale bombing in the post-Sept. 11, 2001, era, the Boston attack killed three people and wounded more than 250 others.

The officials, who spoke on condition of anonymity to describe an ongoing investigation, said Dzhokhar and his older brother, Tamerlan Tsarnaev, who was killed by police as the two attempted to avoid capture, do not appear to have been directed by a foreign terrorist organization.

Rather, the officials said, the evidence so far suggests they were “self-radicalized” through Internet sites and U.S. actions in the Muslim world. Dzhokhar Tsarnaev has specifically cited the U.S. war in Iraq, which ended in December 2011 with the removal of the last American forces, and the war in Afghanistan, where President Obama plans to end combat operations by the end of 2014.

Also coming out today: Tsarnaev says his older brother Tamerlan was the driving force behind the attack. This was already becoming clear, but now we have confirmation from the suspect himself.

A U.S. government source tells CNN that in preliminary interviews with the Boston Marathon terrorist attack bombing suspect, Dzhokhar Tsarnaev has told law enforcement that no foreign terrorist groups were involved in the incident; there was an online component to their radicalization - through watching videos, not through online communication; and that older brother, Tamerlan, was the driving force behind the planning and execution of the attacks.