* Miners and financials lift the index

* Q2 GDP data likely to show record contraction

* NZ bourse marks best day in over a week

Sept 2 (Reuters) - Australian shares were set for their best session in three weeks on Wednesday, boosted by miners and financials, as upbeat U.S. manufacturing data and factory expansion in China fuelled optimism over an economic recovery.

The S&P/ASX 200 index rose as much as 1.5% to 6,043.90 by 1245 GMT, its biggest intraday percentage jump since Aug. 10.

On investors' radar, is the country's second-quarter GDP data due later in the day, which is widely expected to show a record contraction.

Sparking hopes of a rebound in economic activity in the coming months was better-than-expected U.S. manufacturing activity data and a report out of China on Tuesday showing factory activity expanded at the fastest rate in nearly a decade in August.

That helped Wall Street's benchmark S&P 500 index close at a record high overnight.

China is Australia's biggest trading partner and two-way trade between the two countries was worth A$235 billion ($172.73 billion) last year.

Australian miners, reliant on exports to China, were the biggest boosts to the index, jumping as much as 2.6%.

Heavyweight iron ore miners BHP Group and Rio Tinto were among the top gainers, adding 3.4% and 2.2%, respectively.

The financials sub-index rose 1.2%, lifted by top two lenders Commonwealth Bank of Australia and Westpac Banking Corp, each advancing to about 1%.

Among the biggest gainers on the index was AMP, up 6.2%, after the country's biggest wealth advisory firm said it was putting all its assets under review, setting in motion a potential sale or break-up of the company.

Across the Tasman Sea, New Zealand's benchmark S&P/NZX 50 index rose as much as 0.6% to 11,860.920 and is on track for its best day in over a week.

Financials and utilities were the top gainers in the index, with NZ-listed shares of Westpac Banking Corp jumping 1.4% and Meridian Energy adding 2.1%.

($1 = 1.3605 Australian dollars)

(Reporting by Sameer Manekar in Bengaluru; Editing by Amy Caren Daniel)