WASHINGTON: China has been very aggressive in gaming the trading system to its advantage and to the disadvantage of other countries, particularly America, President Barack Obama said today, as the US Senate advanced a legislation to penalise Beijing for undervaluing its currency.

"We've been seeing a remarkable transformation of China over the last two decades. And it's helped to lift millions of people out of poverty in China. We have stabilised our relationship with China in a healthy way," Obama said at a news conference here.

"But what is also true is that China has been very aggressive in gaming the trading system to its advantage and to the disadvantage of other countries, particularly the United States," Obama said at a news conference here.

Currency manipulation is one example of it or at least intervening in the currency markets in ways that have led their currency to be valued lower than the market would normally dictate, he argued.

"It is indisputable that they intervene heavily in the currency markets and that the RMB, their currency, is lower than it probably would be if they weren't making all those purchases in the currency markets to keep the RMB lower," Obama said.

"That makes their exports cheaper and that makes our exports to them more expensive. So we've seen some improvement, some slight appreciation over the last year, but it's not enough. It's not just currency, though. We've also seen intellectual property, technologies that were created by US companies, with a lot of investment, a lot of up-front capital, taken, not protected properly, by Chinese firms," Obama said.

But quickly pointed out that the US has pushed China on that issue as well.

"Ultimately, I think that you can have a win-win trading relationship with China. I'm very pleased that we're going to be able to potentially get a trade deal with South Korea. But I believe what I think most Americans believe, which is trade is great as long as everybody's playing by the same rules," he said.

Referring to the question on legislations in this regard in the Congress, he said: "I don't want a situation where we're just passing laws that are symbolic knowing that they're probably not going to be upheld by the World Trade Organisation, for example, and then suddenly US companies are subject to a whole bunch of sanctions."