Hong Kong tycoons Li Ka-shing and Lee Shau-kee have signed on as cornerstone investors in the Hong Kong portion of Agricultural Bank of China Ltd.'s initial public offering, with each subscribing to HK$1 billion (US$129 million) worth of shares in the lender, people familiar with the situation said Tuesday.

The investments by Li, chairman of developer Cheung Kong (Holdings) Ltd. (0001.HK), and Lee, chairman of Henderson Land Development Co. (0012.HK), in China's third-biggest bank are subject to a one-year lock-up period, according to the people, who declined to be named.

Hong Kong public offerings are often announced with subscriptions by cornerstone investors as a way to boost investor interest and the city's billionaires are often leading candidates for such investments, as are overseas sovereign-wealth funds.

Cheung Kong couldn't immediately be reached for comment. Henderson Land declined to comment.

The people said AgBank plans to sign up more cornerstone investors in the IPO in Hong Kong and Shanghai, which could become the world's largest by raising as much as US$28 billion, in coming days. The potential investors are based in the Middle East, Europe, Australia, and Japan, they said.

Singapore state investment company Temasek Holdings, Middle Eastern sovereign-wealth funds Qatar Investment Authority and Kuwait Investment Authority have agreed in principle to become cornerstone investors in the IPO, other people familiar with the situation told Dow Jones Newswires over the weekend.

Temasek will invest around US$200 million, one of those people said Tuesday, adding a final decision on the investment is expected some time this week.

To ensure the success of the IPO, AgBank is in talks to lock in cornerstone investors for around 30% to 40% of the entire offering, people familiar with the situation said earlier.

Dutch financial services firm Rabobank, which has agreed to form a strategic partnership with AgBank, would also be a "logical" cornerstone investor, a person familiar with the deal said last week.

Agricultural Bank started the pre-marketing process for the IPO in Hong Kong and Shanghai on Monday. The lender has slightly trimmed the US$20 billion-US$30 billion range it had earlier expected to reap from the deal to US$18.9 billion-US$28 billion.

China's pension fund is the bank's sole strategic investor, having bought shares before the IPO was launched. In the prospectus issued last week, AgBank said the pension fund owns a 3.7% stake in the bank, and China's sovereign-wealth fund and Ministry of Finance the remainder.

AgBank has long been considered the weakest of China's big banks with a bigger legacy of bad loans that delayed its coming to market. But as the last of China's Big Four banks to list, it offers a rare opportunity for those investors still willing to bet on China's long-term growth.

AgBank announced a group of 10 investment banks to underwrite the deal in April, among which China International Capital Corp. will handle both the A- and H-share portions.

Morgan Stanley (MS), Goldman Sachs Group Inc. (GS), J.P. Morgan Chase & Co. (JPM), Deutsche Bank AG (DB), Macquarie Group Ltd. (MQBKY) and Agricultural Bank's wholly owned investment banking unit, ABC International Holdings Ltd., are the other underwriters for the H-share offering. Citigroup Inc. (C) is a co-lead manager on the Hong Kong IPO.

Citic Securities Co. (600030.SH), Guotai Junan Securities Co. and China Galaxy Securities Co. are the other underwriters for the A-share offering in China.

With the deal approved in both China and Hong Kong, the bank will be on track to list in Shanghai on July 15 and in Hong Kong the following day, people familiar with the situation said earlier.

Agbank is China's third-biggest bank by assets after Industrial & Commercial Bank of China Ltd. and China Construction Bank Corp. ICBC, the country's largest bank by assets, raised $21.9 billion in 2006 in the world's biggest IPO.

-By Yvonne Lee and Joyce Li, Dow Jones Newswires; 852-2802-7002; yvonne.lee@dowjones.com

(Samuel Holmes in Singapore contributed to this article.)