Hagel said because North Korea and Iran have improved their longer-range ballistic missile capabilities, the United States will about double its interceptor system on the West Coast, the Defense Department said in a release.
The defense secretary also cited North Korea's sabre-rattling rhetoric and nuclear bomb testing as reasons for bolstering U.S. anti-missile resources.
"The United States has missile defense systems in place to protect us from limited ICBM attacks, but North Korea in particular has recently made advances in its capabilities and is engaged in a series of irresponsible and reckless provocations," Hagel said.
He said the U.S. military will deploy 14 more ground-based interceptors at Fort Greely, Alaska, and Vandenberg Air Force Base in California, raising the totals from 30 to 44.
Hagel said the United States would also deploy additional advanced radar equipment in Japan to provide improved early warning and tracking of any missile launched by North Korea at the United States or Japan.
Hagel said the Defense Department is completing environmental impact studies for a potential new interceptor site in the United States, including two sites on the East Coast and one on the West. No decision has been made whether to proceed with construction of a new site, however.
In addition, Hagel said plans were under way to restructure the military's land-based SM3-2B missile program in Europe to improve the U.S. ability to counter missile threats from Iran and North Korea in a cost-effective way, Hagel said.
"The American people expect us to take every necessary step to protect our security at home and U.S. strategic interests abroad," he said. "But they expect us to do so in the most efficient and effective manner possible."