Three Vietnamese-Americans were convicted on terrorism charges Friday after being accused of trying to take over radio airwaves and call for an uprising against Vietnam's communist government.

A judge sentenced the Americans and four Vietnamese to 15 months in prison, with credit for time served. They all are expected to be freed within one month, and the Americans required to leave the country within 10 days of their release.

The defendants had been jailed without charges for more than a year, prompting Washington to pressure Hanoi to move forward swiftly and fairly.

President Bush and Secretary of State Condoleezza Rice plan to visit Vietnam next week for the 21-nation Asia-Pacific Economic Cooperation summit. Both countries had been eager to resolve the case before Vietnam's biggest-ever international event begins.

The defendants faced punishments ranging from 12 years in prison to execution, but prosecutors sought lesser terms, saying the defendants had repented and had no previous criminal records.

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It is highly unusual for Vietnam to give a lenient sentence for national security crimes, especially in such a high-profile case. But the quick resolution to the diplomatically sensitive trial could end a distraction from APEC and Vietnam's entrance into the World Trade Organization, which was approved this week.

All on trial were accused of plotting to smuggle radio equipment into Vietnam to broadcast a call for a revolution to topple the government.

An indictment said the scheme was hatched by the Government of Free Vietnam, a California-based organization that the Vietnamese government considers a terrorist group.

It is one of many anti-communist groups founded by Vietnamese refugees in the United States. Many of its leaders are soldiers of the former South Vietnamese Army who fled Vietnam after the war ended in 1975.

The Government of Free Vietnam group is run by Chanh Huu "Tony" Nguyen, who is wanted in Vietnam for failed plots to bomb the Vietnamese Embassy in Thailand and buildings in Vietnam.

Nguyen, a permanent U.S. resident, was arrested at Vietnam's request in April while traveling in South Korea. He was held for three months before being released to the U.S.

Presiding Judge Vu Phi Long said the crimes were "particularly serious and encroach on national security" and deserved severe punishment. But he said the defendants deserved leniency because they had expressed remorse, had no previous criminal records and were politically naive.

He said they had been dragged into the scheme by Chanh and his associates.

Prosecutors say the defendants convicted Friday set up an adoption agency in Cambodia as a front to disguise their plans. Authorities seized their equipment, including 14 radio transmitters, which had been smuggled into the southern Vietnamese province of An Giang.

Those found guilty Friday were: Thuong Nguyen Foshee, 58, of Orlando, Fla.; Le Van Binh, 31, of Tampa, Fla.; and Huynh Bich Lien, 51, of San Gabriel, Calif.; Vietnamese nationals Tran Dat Phuong, 65; brothers Ho Van Giau, 59, and Ho Van Hien, 38, and Cao Tri, 35. Cao Tri is also a U.S. resident.

Under questioning from the judge, some of the defendants acknowledged carrying radio equipment to Cambodia on behalf of the Government of Free Vietnam, while others described themselves as employees at an adoption agency.

Lien said she was not a member of the Government of Free Vietnam, but had gone to work for USIM, a charity in Cambodia that helped arrange adoptions of Cambodian kids for Americans. She said she knew Chanh was associated with USIM but that all she did was help take care of children.

Two representatives of the U.S. consulate attended the trial.

On display near the court house entrance were two tables covered with radio equipment the defendants had allegedly planned to use.

The case has attracted attention from Sen. Mel Martinez, R-Fla., who raised the issue with the Bush administration and reportedly blocked a key vote in Congress that would normalize trade relations between the former foes.

The vote is of great importance to Vietnam. Without it, U.S. companies will not be able to enjoy all the benefits of Vietnam's new WTO agreement.

Bush had been hoping to get the bill approved before he came to Hanoi for the APEC summit. Resolution of the terrorism case might increase his chances, although Congress will only be in session briefly before he departs next week.