April 10 (Reuters) - Nike ( NKE ) is investigating a design issue affecting several national team kits ahead of this year's soccer World Cup, British media reported on Friday, after problems with the shirts became visible during last month's international break.

Bulging around the shoulder seams was visible on shirts worn by teams including England, France and Uruguay during the international window.

A Nike ( NKE ) spokesperson told The Guardian newspaper that the company had identified a "minor issue" with the kits, adding that performance was unaffected but the "overall aesthetic is not where it needs to be."

The issue is present on both match shirts worn by players and replica versions sold to supporters, according to the BBC, with some fans raising concerns.

The American sportswear giant produces kits for a number of World Cup teams, including co-hosts the United States and Canada, as well as Brazil, the Netherlands and Croatia.

The kits have been designed with cooling technology to help players cope with high temperatures expected at the tournament, which kicks off on June 11 and is also co-hosted by Mexico.

The issue comes as the struggling company faces questions over its product innovation and works through excess inventory after a string of weak earnings.

Chief Executive Elliott Hill has pledged to refocus Nike ( NKE ) on core sports, and the company said on Friday it had appointed Andy Caine as chief innovation officer.

Nike ( NKE ) did not immediately respond to a Reuters request for comment.