UPDATE 2-Cemex sells Australian assets to Holcim

* Cemex completes A$2.02 billion sale

* Money crucial to Cemex's $15 billion refinancing plan (Adds Holcim comment)

MONTERREY, Mexico Oct 1 (Reuters) - Mexico's Cemex, the world's No. 3 cement maker, said on Thursday it completed the sale of its Australian assets to Switzerland's Holcim for over $1.7 billion in a boost for its debt repayment efforts.

Cemex (CMXCPO.MX) (CX.N) announced the A$2.02 billion ($1.76 billion) sale to Holcim (HOLN.VX) in June and was forced to exit one of the world's fastest growing markets, receiving only about half the price it had paid for the assets in 2007.

"The proceeds from this sale ... will be used to reduce debt," Cemex said in a statement.

Holcim confirmed the deal in a separate statement and said the assets were now part of the company, trading under the name Holcim (Australia) Pty Ltd.

The completion of the deal helps Cemex repay its $15 billion debt and is a likely relief to investors after another Cemex asset sale in Europe fell through earlier this year.

Cemex suffered from a poorly timed purchase of Australia's Rinker in 2007, just before the global financial crisis. The Monterrey-based company has struggled to repay the short-term loans it took on to pay for Rinker but won a refinancing deal in August to stretch out payments until 2014.

Many investors balked at Cemex selling its assets to a direct competitor such as Holcim, which is using the Australian assets to grow in cement as well as aggregates and ready-mix concrete.

But shareholders have for now chosen to focus on Cemex's revival, sending its stock up by more than a quarter since the Aug. 14 debt deal announcement.

Cemex, which also competes with France's Lafarge (LAFP.PA), looks to be well placed to cover its obligations until 2011 after it sold $1.78 billion in shares this month in a global offering to raise capital.

In one of Mexico's biggest stock offerings, Cemex priced 1.3 billion Ordinary Participation Certificates and American Depositary Receipts at $12.50 each, or 16.64825 Mexican pesos. The company also sold another 195 million shares in an over-allotment option.

Many investors see shares in Cemex climbing further over the next few months as much of the uncertainty hanging over the company has eased with the refinancing deal and the share sale.

Cemex shares were off 1.1 percent to 17.30 pesos in Mexican trading. (A$1 = 87.2090 U.S. cts) (Reporting by Robin Emmott and Gabriela Lopez, editing by Gerald E. McCormick)