Asian markets rose and the dollar remained subdued against the yen on Wednesday ahead of a US Federal Reserve meeting most economists expect will deliver fresh stimulus to kickstart the economy.

Comments from China's prime minister hinting at new monetary easing also provided a fillip, while traders are confident of a positive verdict in Germany as judges are due to rule on whether Berlin can legally take part in the eurozone's bailout fund.

Tokyo surged 1.46 per cent by the break, with much better-than-expected July economic data helping to lift sentiment, while Hong Kong jumped 0.94 per cent, Sydney advanced 0.80 per cent, Shanghai climbed 0.16 per cent and Seoul added 1.39 per cent.

The US Fed will later begin its two-day policy meeting, after which there is a wide expectation it will unveil new measures to spur growth, with most analysts tipping a third round of bond-buying, or quantitative easing.

On Wall Street the Dow was up 0.52 per cent and the S&P 500 rose 0.31 per cent while the tech-rich Nasdaq was flat.

Adding to buying incentives were data showing the US trade deficit was virtually unchanged in July from June, an unexpected reading although the figures showed imports and exports dropped due to a global slowdown.

"Market sentiment is very positive," said Brett McGonegal, chief executive officer at Reorient Financial Markets in Hong Kong.

"Once people get into the buying mood it is not a one-day event, we could have an overall buying appetite that could absorb a shock," he told Dow Jones Newswires.

But with the likelihood of more dollars flooding the market the currency retreated in New York from recent highs against the yen and stayed weak in Tokyo.

In early Asian trade it bought 77.91 yen, against 77.73 yen in New York late Tuesday. In Asia on Tuesday the greenback was buying around 78.20 yen.

However, also weighing on the unit was a warning from Moody's that it would downgrade the United States' AAA credit rating if lawmakers did not get the country's debt situation in order.

Late Tuesday Chinese Premier Wen Jiabao said the world's number two economy 'was showing signs of stabilising' and would likely meet the 7.5 per cent growth the government set for the year.

"We will, according to economic trends, make full use of the advantage of having relatively big space for fiscal and monetary policy (moves)," he said.

Wen later emphasised that despite a slowdown in government revenues, the government has about a one trillion yuan ($158 billion) surplus on its balance sheet and around 100 billion yuan in what he called 'stability and adjustment funds'.

The government 'will not hesitate to use' such money, he following a speech to the World Economic Forum in the eastern city of Tianjin.

The comments suggested Beijing was ready to announce new measures to boost spending in China -- a key driver of regional growth -- such as lowering the amount of money banks must keep on reserve, or even cutting interest rates.

In Germany later on Wednesday eight judges of the country's Constitutional Court will rule on the legality of the European Stability Mechanism (ESM) set up to help under pressure nations.

While the court has a history of ruling in favour of steps towards greater European integration, a negative decision could blow the entire euro project apart, owing to Germany's key role in financing future rescues.

On currency markets the euro bought $1.2846 and 100.08 yen in Asia, from $1.2848 and 99.88 yen in New York.

New York's main contract, light sweet crude for delivery in October, shed eight cents to $97.09 a barrel and Brent North Sea crude for October fell six cents to $115.34.

Gold was at $1,734.50 at 2.50 am GMT compared with $1,730.35 on Tuesday.