But the trend could come to an end as summer draws to a close. Alibaba is expected to make one of the largest public offerings ever in August and smaller mainland technology firms are reportedly rushing to squeeze into the market before then.

Insiders said the Alibaba deal, which could raise up to US$20 billion, was likely to be as much as New York investors could stomach from the mainland in the second half of the year.

"Once Alibaba goes out, there may not be a lot of liquidity in the market," one lawyer handling mainland listings in New York told the . "How it's going to look in the second half is up for debate."

Appetite for mainland companies in Hong Kong was subdued in the first half of the year compared with the latter half of last year, when several large banks went public.

The failed offering of pork processor WH Group, known as Shuanghui International before it bought out US firm Smithfield Foods in September, highlighted the weak investor sentiment.

Overseas offerings in the first half increased mildly on last year, data compiled by Reuters showed. More than 90 firms issued shares offshore during the period, raising about US$16.8 billion. Just 51 companies issued shares worth US$14.8 billion in the first half of last year.

The Hong Kong market has waned since several large mainland banks and financial institutions went public in the city in the second half of last year.

China Everbright Bank raised about US$3 billion in December, though the share price fell on its debut. China Cinda Asset Management raised about US$2.5 billion the same month.

The weak demand for mainland listings abroad has been balanced out with strong demand for offshore bonds issued by mainland firms and a willingness by foreign banks to lend in US and Hong Kong dollars.

The market for mainland offshore debt is booming. In the first half, 252 mainland firms issued bonds abroad, raising a total of US$73.3 billion, compared with the 192 firms that raised US$47.9 billion last year, data showed.

"One reason you see a strong build-up of bond activity is because the [listing] market has been somewhat lacklustre," said Clifford Lee, head of fixed income at DBS Bank in Singapore.

Many of the players issuing US or Hong Kong dollar-denominated debt in the global market are large, state-owned enterprises and property developers rather than the technology outfits tapping the equities markets.

Offshore syndicated borrowing in the first half of this year was stable and that trend was set to hold in the second half, said Atul Sodhi, head of loan syndication in Asia-Pacific for Credit Agricole.

Mainland companies borrowed roughly US$13.3 billion from offshore lenders in the first half, according to Dealogic, an 18.4 per cent increase on last year.

Those firms moved offshore to raise cheaper foreign currency after government regulations curbed onshore US dollar lending in May. Worries over the health of mainland banks, soaring debt at local governments and questionable non-performing loan data are also pushing banks offshore.

"The news flow coming out of the mainland has been mixed and it makes sense for borrowers to access diversified sources of lending," Sodhi said.

Rating agency Moody's Investors Service warned Hong Kong banks last week on their exposure to mainland borrowers. The city's exposure to the mainland grew 29 per cent last year and accounted for 20 per cent of its total banking assets, or HK$2.3 trillion, at the end of the year. The International Monetary Fund issued a similar warning earlier this year.