* CRRC, no. 1 global train maker, in XpressWest project

* Project seen worth $5 bln, may open US, other markets

* Giant CRRC stepping up plans to boost overseas sales (Adds details of Xi's visit, other business deals)

By Brenda Goh

BEIJING, Sept 17 (Reuters) - A unit of China's CRRC Corp , the world's biggest train maker by revenue, on Thursday joined a group of its domestic peers in agreeing a deal to help build a high-speed link from Las Vegas to Los Angeles, underlining the rail giant's lofty overseas ambitions.

Announced in a joint statement by the Chinese firms and U.S. partner XpressWest at a government forum in Beijing, the deal is the latest in a series of deeper Sino-American business ties to be unveiled before President Xi Jinping visits the United States next week. Computer maker Dell Inc said it will invest $125 billion in China, and new bilateral investment treaty offers have been exchanged.

CRRC, formed from a state-driven merger of China's two largest train makers, is among a large group of the country's rail firms that has inked an accord for the project with XpressWest, a venture set up by Las Vegas-based hotel and casino developer Marnell Companies. Investment terms weren't disclosed.

Gary Wong, a Hong Kong-based analyst at brokerage Guotai Junan, estimated that the project could be worth $5 billion. He said that although it would likely offer the many Chinese firms involved little financial benefit, it was significant for their long-term goals.

"If this opens up the U.S. market for them, opportunities for future expansion will increase. And if (their technology) is used in the United States, it will be easier for them to sell to other countries," he said.

CRRC is leading China's aggressive pursuit of overseas high-speed rail deals in competition with traditional suppliers such as Germany's Siemens AG and France's Alstom SA . Beijing recently clinched contracts in Russia, although it has faced hurdles in Mexico and Indonesia due to bureaucratic flip-flops in those countries.

US POTENTIAL

The United States is a key target for China's rail industry, even though policymakers have been split over the need for high-speed rail and some have taken a dim view of Chinese involvement in potentially strategic deals. Most of a dozen or so U.S. projects lined up have struggled to gain traction, leaving the country far behind Europe and Asia in this area.

XpressWest won the green light for the 230-mile high-speed line linking Los Angeles to Las Vegas in 2011 and applied for a federal loan in 2010, according to the company's website. It did not say whether its loan application had been successful.