WASHINGTON — After six years at war, some Army National Guard units are still struggling with less than half the equipment they need to defend the homeland, and it will take an extra $13 billion over the next five years to get them 90 percent of what they need, the top Guard general said Wednesday.

Lt. Gen. Steven Blum, chief of the National Guard, said that while Guard units heading to Iraq and Afghanistan have all the equipment they need, those at home have as little as one-third of the needed trucks, radios and other gear.

Blum said all units at home are short at least 30 percent of the equipment they need. The low end is 33 percent, and 50 percent is the average, he said.

Blum has sounded the same alarm on Capitol Hill for several years, warning that Guard units sapped by deployments to Iraq and Afghanistan often end up with equipment worn out by war or, in many cases, simply left on battlefields.

In addition to the $21 billion already budgeted for the next five years, Blum said the Army Guard will need another $13.1 billion for equipment, and the Air Guard will need about $8.8 billion for equipment over that time.

That money, he said, would give the Guard 90 percent of the needed equipment, which would be an acceptable level.

In the event of a sudden natural disaster or terror attack, Blum said, the Guard “must have the equipment in their hands when the event happens so they can immediately respond… There’s no time to start moving it from neighboring states and drawing it from consolidated sites as some people have suggested.”

Right now, Blum said, about 18 percent of the Army soldiers in Iraq are Guard members — just slightly lower than the percentage of the soldiers serving in Afghanistan. That number is dramatically lower than Guard force levels during part of 2005, when Guard soldiers made up about 50 percent of the force in Iraq.