San Francisco ? An American activist who was jailed in Vietnam for more than a month on suspicion of plotting against the communist government said Friday he would continue his fight for democracy in his native country.

“I plan to keep on fighting as long as possible,” Cong Thanh Do said at a news conference. “In Vietnam, the society has changed a lot, but the political system is still under a political dictatorship.”

Appearing with his wife and children, Do looked frail and tired. He arrived at San Francisco International Airport on Thursday night, after the Vietnamese government deported him without comment. He said he still felt weak after staging a hunger strike for 38 days, but was relieved to be back in the U.S.

Police arrested Vietnamese-born Do on Aug. 14 while he was on vacation with two Vietnamese citizens in the south-central city of Phan Thiet. Police accused them of setting up the anti-government People’s Democracy Party.