(updates with fresh quotes, reaction)

By Adrian Croft

LONDON, Jan 17 (Reuters) - British Prime Minister Gordon Brown heads to India and China on Thursday to try to boost trade with their fast-growing economies and offset the impact of the credit crunch that is hitting growth elsewhere.

The economies of China and India, where domestic demand is expected to play a bigger role than in the past, are expected to power ahead this year as growth in Europe and the United States takes a knock.

That makes the Asian giants increasingly important trade and investment partners to help keep Britain's economy growing, and Brown wants a strategic long-term partnership with China.

"I can see in the next few years a 50 percent increase in our trade with China. I can see thousands of British jobs, perhaps tens of thousands of British jobs, over a period of time developing from this new relationship," Brown told ITV News.

Britain sees opportunities to sell more services to China in areas such as financial services, insurance and retail. Chinese officials also see scope for greater cooperation on clean energy technologies where Britain has expertise.

Brown insists Britain is well placed to weather the global financial crisis but there are signs the decade-long house price boom is grinding to a halt and economic growth is slowing.

That raises the risk of a politically damaging economic downturn in the run-up to the next national election that Brown, a former finance minister, must call by mid-2010 at the latest.

DIFFERENCES ON IRAN, DARFUR

While Britain is keen to promote trade with China, the two countries do not always see eye-to-eye on Iran, Myanmar or the conflict in Sudan's Darfur province. Brown said this week he would continue to press Beijing on human rights issues.

"He will be raising human rights," Brown's spokesman confirmed on Thursday. But the premier would not be broaching any specific cases, he added.

Human Rights Watch said in an open letter to Brown that he should use his visit to press Beijing on the issue in the run-up to the Olympics.

A Chinese diplomat said it was very important for Britain and China, as permanent members of the United Nations Security Council, to sit down regularly and discuss international issues such as Iran, Darfur, Myanmar and the Middle East.

Western politicians and rights groups have accused China in the past of selling Khartoum arms that end up in Darfur and of fending off stronger U.N. Security Council resolutions.

Brown said on Wednesday he had talked with Chinese Premier Wen Jiabao about Darfur and would have talks with him in China about stepping up pressure for a peaceful settlement.

On Iran, Britain has supported its ally, the United States, in pressing for new sanctions against Tehran's nuclear activities, but China wants a negotiated solution.

And unlike Britain, China has been reluctant to criticise Myanmar's military rulers publicly.

Some business contracts are expected to be signed during Brown's first visit to Beijing as prime minister.

But the Chinese diplomat said he would be surprised if they were comparable to the near $30 billion of deals French President Nicolas Sarkozy oversaw during his visit in November.

Britain has been the biggest European Union investor in China over the past few years but it has been less successful than European rivals in exporting to China. (Editing by Paul Majendie and Ralph Boulton)

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