Texas police have decided not to charge a 14-year-old Muslim boy arrested for bringing a homemade clock to school.
Officials at MacArthur High School in Irving alerted police because they thought the device was a "hoax bomb".
Ahmed told reporters it was "very sad" that his teacher thought his clock was a threat.
"I built a clock to impress my teacher but when I showed it to her she thought it was a threat to her. I'm very sad that she got the wrong impression of it."
At the same news conference on Wednesday afternoon, Ahmed announced he plans to transfer schools.
Ahmed's father Mohamed Elhassan Mohamed, who is originally from Sudan, praised his son's ingenuity, saying he fixes everything around the house, including his father's phone and computer.
"He's a very smart, brilliant boy and he said he just wanted to show himself to the world," he said.
The police have rejected the claim made by Ahmed's family that he was detained because of his name.
"We have always had an outstanding relationship with the Muslim community," Irving Police Department chief Larry Boyd said on Wednesday. "Incidents like this present challenges. We want to learn how we can move forward and turn this into a positive".
The boy was placed in handcuffs and fingerprinted. He was released after it was determined there was no threat.
"Cool clock, Ahmed. Want to bring it to the White House? We should inspire more kids like you to like science. It's what makes America great," Mr Obama wrote on Twitter.
The Council on American-Islamic Relations says it is investigating the incident.
Ahmed said that he had made a clock at home and brought it to school to show his engineering teacher.
He said his engineering teacher had congratulated him but advised him "not to show any other teachers".
The teenager said another teacher became aware of it when the device beeped during the lesson.
"She was like - it looks like a bomb," he said.
The homemade clock consisted of a circuit board with wires leading to a digital display.
Later in the day the boy was pulled out of class, interviewed by senior teachers and four police officers, and put into juvenile detention.
The school issued a statement saying it "always ask our students and staff to immediately report if they observe any suspicious items".