WASHINGTON - US anti-ballistic missile systems will cover all of Europe by 2018, a senior Pentagon official said, laying out an ambitious target for defending against a perceived threat from Iran.

"One hundred percent," Bradley Roberts, deputy assistant secretary of defense for nuclear and missile defense policy, said in reply to a question at a hearing of a House of Representatives Armed Services subcommittee Thursday.

Roberts said the Obama administration was putting "proven" sea-based and land-based missile shields into Europe as quickly as possible as part of a revised shield announced last September to any Iranian ballistic-missile strike.