* CSI300 -1.8 pct; SSEC -1.9 pct; HSI -1.3 pct
* Hong Kong market poised to fall for 5th straight day
* Energy, resource shares lead declines
SHANGHAI, May 6 (Reuters) - China stocks dropped nearly 2 percent on Friday morning, erasing this week's gains as the market's rebound since early March risks unravelling amid further corrections in the commodities market and fresh signs of stress with bonds.
Hong Kong shares also fell, with the benchmark index on track to decline for a fifth day and have its worst weekly performance in three months.
China's benchmark CSI300 index dropped 1.8 percent, to 3,156.18 points by lunch break, while the Shanghai Composite Index lost 1.9 percent, to 2,942.46 points.
If the indexes fall lower in afternoon trade, the market will register its third consecutive weekly loss, and further show fatigue following its strong rebound in March.
Analysts say investor patience is wearing thin as the Shanghai index has failed to stay above the psychologically key 3,000 mark in recent weeks, while the economy remains fragile.
"If the market cannot make a breakthrough upward, then going down would be the natural choice, given the lack of good news on the fundamental front," said Chang Chengwei, analyst at Hengtai Futures.
Chang also attributed the weakness in stocks to drops in China's commodities market on Friday, and fears that more companies need to sell shares to raise enough money to pay debts.
On Thursday, a Chinese fertiliser producer defaulted on bond payments, the latest casualty of China's slowing economy, and adding stress to the credit market.
In Hong Kong, the Hang Seng index dropped 1.3 percent, to 20,183.43 points, while the Hong Kong China Enterprises Index lost 1.6 percent, to 8,493.27.
Stocks fell across the board in China and Hong Kong, with energy and resources shares leading the decline in both markets.
Reporting by Samuel Shen and Pete Sweeney; Editing by Richard Borsuk