WASHINGTON — Petty Officer 3rd Class Jeonathan Zapata was excited to finally become an American citizen. But he was even more thrilled when the first person to congratulate him was the commander in chief.

"I never thought I’d get to do that in my life," the 22-year-old from Nicaragua said. "It’s such a big honor. … I’m so proud."

Zapata was one of 24 servicemembers who took part in a military naturalization ceremony Friday at the White House. The new citizens, representing all five services and 18 countries, were sworn in by Department of Homeland Security Secretary Janet Napolitano and welcomed as "fellow Americans" by President Barack Obama.

"You’ve not merely chosen to live in this country. You’ve chosen to serve this country," he told the new citizens. "In the service that you’ve rendered, the sacrifices you’ve endured … you’re part of a larger story. America’s story."

Under changes in immigration law in 2002, foreign citizens who become permanent U.S. residents and join the military need only one year of service to qualify for citizenship. During wartime, they need only one day of service to qualify. Without serving, foreign residents must wait five years before they become eligible.

Troops at Friday’s ceremony were a mix of longtime resident aliens and new immigrants. Zapata was an infant when his mother first arrived in America, and he grew up with a love of both the country and the military.

He enlisted at 18 and spent several years stationed in Japan on board the USS Kitty Hawk. Just last month he returned to the U.S. after a tour on USS Theodore Roosevelt supporting missions in Afghanistan.

Army Spc. Chryshann Pierre moved to America with her family at age 9, but never worked to change her citizenship until joining the Army two years ago. She saw the Army as a way to provide for her family, but found she loved the people and the work.

Her commanders at Fort Campbell in Kentucky didn’t tell her any of Friday’s ceremony details until she arrived in town a day earlier.

"When they told me that the ceremony was at the White House, I started tearing up," she said. "When I tell my oldest son that his mother became a citizen and met the president, he’ll be so proud. He’s gonna be walking around school bragging about his mom at the White House."

Obama singled out both Zapata and Pierre during the event, mentioning Zapata’s lifelong desire to serve and Pierre’s unexpected love of boot camp and hard work (and eliciting a quick "hooah" from the soldier).

He also awarded the annual Outstanding American by Choice award to Peter Lemon, a Canadian immigrant who served in the Army and was awarded a Medal of Honor for actions in the Vietnam War.

After the ceremony the president spent time with several of the new citizens, thanking them for their service. Zapata said he was overwhelmed by the experience.

"I never thought I’d get to shake the president’s hand," he said. "But I got to today."

"I shook it twice," Pierre said, smiling.