Maccarinelli (right) was never in trouble against the American

The Swansea fighter was in powerful form from the start and the bout was stopped with 25 seconds still remaining in the opening round.

Gunn was left bloodied after a series of strong shots from Maccarinelli.

It was Maccarinelli's second defence of the title he won against Marcelo Dominguez last July.

He maintained his concentration and boxed neatly behind a heavy jab while he waited for his chance. Having caused problems with a trademark left hook, he unleashed some powerful shots and injured the challenger's nose.

Despite being granted temporary respite by the referee, it was simply delaying the inevitable and the contest was soon brought to an end, leaving the Welshman on track for a unification bout.

"I have stepped up to the next level now and I am looking to unify the belts. It doesn't matter which one of the champions I get, but I just can't wait," he said.

"I caught him with some good shots before the stoppage and credit to him, he stayed on his feet when lesser men would have folded.