FOXBOROUGH, Mass. — Coach Bill Belichick said Saturday he is convinced that the New England Patriots broke no league rules in using underinflated footballs in the first half of Sunday’s victory against the Indianapolis Colts in the AFC championship game.

“I believe now 100 percent that I have personally, and we as an organization, have absolutely followed every rule to the letter,” Belichick said during an unscheduled news conference.

The league announced Friday it had determined that the Patriots used underinflated footballs in the first half of their 45-7 victory over the Colts. The NFL said its ongoing investigation had yet to determine whether the Patriots did so deliberately.

Belichick split time detailing a study conducted by the Patriots and defending the team’s actions and reputation.

According to Belichick, the Patriots found in their study that the footballs being exposed to outdoor weather conditions potentially led to them getting deflated below NFL specifications.

“I’m embarrassed to talk about the amount of time that I’ve put into this relative to the other important challenge in front of us,” Belichick said. “I’m not a scientist. I’m not an expert in footballs. I’m not an expert at football measurements. I’m just telling you what I know.”

The NFL declined to comment.

For a coach known for his dour public disposition, Belichick appeared at times impassioned, testy, combative and even a bit bizarre.

He vigorously defended his team’s honor and said he was no “Mona Lisa Vito” of footballs, referencing a character in the 1992 movie “My Cousin Vinny.”

Said Belichick: “At no time was there any intent whatsoever to try to compromise the integrity of the game or to gain an advantage. Quite the opposite. We feel like we followed the rules of the game to the letter in our preparations, in our procedures and in the way that we handle every game that we competitively play in. We try to do everything right. We err on the side of caution.

“It’s been that way now for many years. Anything that’s close, we stay as far away from the line as we can. And in this case, I can say that … we did everything as right as we could do it.”

Under NFL rules, each team supplies the footballs that it uses on offense during a game. The footballs are to be inflated to between 12.5 and 13.5 pounds per square inch of air pressure. The NFL said Friday that the footballs were inspected by game officials prior to last Sunday’s game and found in compliance.

Belichick said Saturday that the Patriots performed a study during the week and found that the methods they routinely use to get the footballs to the texture they want raises the air pressure by one pound per square inch.

The Patriots are scheduled to arrive in Arizona on Monday to face the Seattle Seahawks in the Super Bowl on Feb. 1.

“This is the end of this subject for me for a long time,” Belichick said. “We have a huge game, a huge challenge for our football team. And that’s where that focus is gonna go. I’ve spent more than enough time on this.”

Belichick said he was being “as transparent as I can be on this one. Period.” He also defended his team’s accomplishments staunchly.

“This team was the best team in the AFC in the regular season,” Belichick said. “We won two games in the playoffs against two good football teams – best team in the postseason. And that’s what this team is. And I know that because I’ve been with them every day, and I’m proud of this team.”

Belichick’s defense Saturday even extended to the Spygate scandal. In September 2007, Commissioner Roger Goodell fined Belichick and the Patriots a total of $750,000 and stripped the team of a first-round draft choice for videotaping opposing coaching signals in violation of league rules.

“The guy is giving signals out in front of 80,000 people, OK?” Belichick said Saturday. “So we filmed him taking signals out in front of 80,000 people, like there were a lot of other teams doing at that time, too. But forget about that. If we were wrong, then we’ve been disciplined for that. …

“So it was wrong. We were disciplined for it. That’s it. We never did it again. We’re never gonna do it again. And anything else that’s close, we’re not gonna do either. … Anything that’s even remotely close, we’re on the side of caution.”