China and India are blamed for failure of sanctions on Burma

As lawyers for Aung San Suu Kyi and the American John Yettaw announced plans to appeal against the sentences handed down to them by the Burmese authorities, experts said that action from China and India was vital to putting pressure on the country's junta to change.

The two countries invest millions of dollars in Burma and vie with each other for strategic influence, so a campaign of co-ordinated action has to focus on the Asian giants. China remains a major supplier of arms to the regime and India has previously sold them weapons and equipment.

"India and China are crucial," said David Mathieson, from Human Rights Watch. "In addition to the trade, China is the main political protector of Burma. India, meanwhile, is quite happy to go on being the silent partner."

Aung San Suu Kyi was ordered on Wednesday to spend a further 18 months under house arrest. Mr Yettaw, 53, who swam to the democracy leader's house in May, triggering the charges brought against her, was sentenced to seven years' imprisonment with hard labour.

Their lawyers said yesterday that they would soon launch legal appeals. Ms Suu Kyi's lawyer, Nyan Win, said the National League for Democracy leader had asked him to explore "all legal avenues" to secure her release.

China is Burma's most important trading partner. It invests hundreds of millions of dollars each year in everything from oil and gas to roads and jade and timber extraction. China was estimated to have provided $850m (£514m) of the $980m that was invested in the country last year.

And when Burma has faced intense international criticism, such as after Cyclone Nargis, China has provided the regime with political cover through its seat on the UN Security Council. Even yesterday, as the West directed fierce criticism towards Rangoon and the cautious Association of Southeast Asian Nations voiced disappointment, China offered a defence. Its foreign ministry spokeswoman Jiang Yu said it was time for dialogue: "International society should fully respect Myanmar's judicial sovereignty."

Estimates suggest that trade between India and Burma is worth about $1bn. India has won the right to develop the Burmese port of Sittwe, a major entrepôt for goods and energy.

India is Burma's fourth largest trading partner, behind China, Thailand and Singapore, but that could change as Delhi seeks to counter the mounting influence of Beijing. Along with China and South Korea, India is also a major investor in Burma's Sittwe gas fields, a project that will see the construction of a gas pipeline to China.

Since the late 1990s and the implantation of its "Look East" policy, India has provided crucial political support for a regime that it once criticised. Indeed, in the aftermath of the 1988 democracy uprising in which an estimated 6,000 people were killed, thousands of Burmese fled across the border into India.

Neither India nor China have shown much inclination to change their relationships with Burma. But activists say this should not be an excuse for the West to do nothing. Anna Roberts, from the Burma Campaign UK, said sanctions supposedly introduced by the EU were full of loopholes. "People say sanctions have been ineffective against Burma, but they have been confronted by a collection of ineffective sanctions – sanctions that have failed to hit their target," she said.