WASHINGTON (REUTERS) - An Iowa man was arrested near the White House on Wednesday after driving across the country with a gun and a knife in his car trunk on a self-described mission to go to the executive mansion, the Secret Service said.

R. J. Kapheim, 41, of Davenport, Iowa, walked up to a Secret Service officer on the east side of the White House grounds and "told the officer that someone in Iowa told him to go to the White House," Secret Service spokesman Nicole Mainor said.

Kapheim said he had driven to Washington from Iowa.

When officers searched his car, a 2013 Volkswagen Passat parked a few blocks away on the edge of the National Mall, they found a .30-30 rifle with more than 40 rounds of ammunition and a six-inch knife in the trunk, she said.

Kapheim was taken into police custody and charged with possession of an unregistered firearm, and may face additional charges, Mainor said.