BOSTON (AP) — U.S. Sen. Scott Brown is urging top defense officials to let women serve in front line combat, saying barring women from those units could make it harder for them to rise up the military ranks.

The Massachusetts Republican urged U.S. Defense Secretary Leon Panetta to adopt the changes in a letter Wednesday.

Brown, a 32-year member of the Massachusetts Army National Guard, praised Panetta for creating more opportunities to women in uniform by allowing them to serve closer to the front lines.

But Brown said the changes don’t go far enough.

He said women should be allowed to compete for positions in combat arms units such as infantry, armor, and special operations.

Brown said closing those options could make it harder for women to develop military career paths that would advance them to higher ranks.

Copyright 2012 The Associated Press.