Li Shaomin: "Glad to be getting home"

Li's deportation comes a day after two other American-based academics, Gao Zhan, and Qin Guangguang, were each sentenced to 10 years in Beijing on spying charges.

BBC Beijing correspondent Rupert Wingfield-Hayes says it is no coincidence that Li's release comes before a visit by US Secretary of State Colin Powell on Saturday.

Beijing is keen to make the visit a success and repair ties damaged by the downing of a US spy plane over China four months ago.

Li was convicted earlier this month, but the Chinese authorities said immediately that he would not be jailed.

I am pleased that these cases are now being resolved

Colin Powell

Speaking on Wednesday during a stopover at Tokyo's Narita airport, Li told reporters he was looking forward to going home and seeing his family.

He also said he was grateful to the US Government for its help and support.

Mr Powell, in Vietnam on Wednesday for regional security meetings in Hanoi, said he was "very pleased" at Li's release, but would not be drawn on the jailing of the others.

"We will talk about that this afternoon, I am pleased that these cases are now being resolved," said Mr Powell before he was due to meet Chinese Foreign Minister Tang Jiaxuan.

'Intensive engagement'

The US has been stepping up its efforts to secure Gao Zhan's release on humanitarian grounds.

Colin Powell's visit aims to mend ties with Beijing

Gao, a Chinese sociologist with permanent US resident status, was found guilty of helping Li.

Fellow US resident Qin Guangguang was also sentenced to 10 years for spying.

Unlike Li, neither of them is a US citizen.

"Qin Guangguang and Gao Zhan both collected intelligence for spy agencies in Taiwan, causing a serious threat to China's national security," China's state-run Xinhua news agency quoted the court as saying.

Also sentenced was Chinese citizen Qu Wei, who got 13 years.

US dismay

The US reacted with dismay at the news of the convictions.

A senior American official travelling with Mr Powell said the US had asked to attend Gao's trial, but the request was refused.

"We are concerned about the lack of transparency in the process and the speed with which this was done," said the official, who did not want to be named.

There's not much argument over the evidence, because Gao Zhan admits that she did these things - what we need to sort out is whether these things constituted crimes

Bai Xuebiao, Gao's lawyer

Gao's trial lasted four hours according to one of her lawyers, Bai Xuebiao.

Mr Bai said he had asked for Gao, 39, to be released for medical care for a heart condition, but had little idea if his request would be granted.

Gao's lawyers said the only evidence the government could produce against her was that she had photocopied articles from official Chinese Government publications about relations between China and Taiwan.

Her husband Xue Donghua has vowed not to rest until she is released.

"I am depressed. I am surprised. But I still have hope," he said.

BBC Washington correspondent Nick Bryant says the hope in Washington is that Gao will be released before Mr Powell's visit.

Gao, who works at the American University in Washington, was detained on 11 February at Beijing's airport during a family trip to China.

Her fellow defendant, Qin Guangguang, a US-based pharmacist who previously studied at the University of Michigan and Stanford University, was detained in December and has worked for a Chinese-American joint venture pharmaceutical company UMIC.

Two other US-based academics in detention are Wu Jianmin, 46, a Chinese-born US citizen arrested in December, and Liu Yaping, a US-based Chinese citizen arrested in March.