* Cable & Wireless says discussing possible cash-and-stock offer
* Cable & Wireless shares soar 20.7 pct
* Deal could expand Liberty's foothold in Caribbean
* 'King of Cable' John Malone backs both companies (Adds Liberty Global statement)
By Mamidipudi Soumithri and Devika Krishna Kumar
Oct 22 (Reuters) - Liberty Global Plc is in talks with Cable & Wireless Communications Plc about a potential deal to unite two companies backed by billionaire cable pioneer John Malone and extend Liberty's reach in the Caribbean.
Cable & Wireless, valued at slightly more than 3 billion pounds ($4.6 billion) as of Thursday's close, said talks were under way regarding a possible cash-and-stock bid by Liberty. It said they were not certain to result in an offer.
Liberty Global confirmed the discussions. According to UK law, it has until Nov. 19 either to make an offer or to announce that it does not intend to buy the company.
Based in London, Cable & Wireless describes itself as "the go-to player in the Caribbean and Latin America". It introduced the first telegraph services to the region in the 1870s, the company says on its website.
The Wall Street Journal first reported the talks on Thursday, citing unnamed people familiar with the matter. It said the deal could be worth more than $5 billion and could be reached by early November. (on.wsj.com/1RqEOvS)
Liberty is back on the hunt for acquisitions less than a month after it abandoned talks with Vodafone Plc about a swap of business assets in Europe's converging mobile phone, broadband and TV markets.
The companies could not agree on valuations.
Malone, the U.S. 'King of Cable', acquired a stake of about 13 percent in Cable & Wireless this year after the company bought Columbus International, a privately owned fibre-based telecoms provider that he backed.
Liberty Global, the owner of pay-TV company Virgin Media, also raised its stake in ITV to 9.9 percent in July but said it did not intend to make an offer for Britain's biggest free-to-air commercial TV firm.
Cable & Wireless had about 3.7 million mobile subscribers, 1.1 million fixed-line subscribers and 388,000 broadband customers as of March 2014, according to its website.
London-listed shares of Cable & Wireless soared 20.7 percent on Thursday to close at 70 pence. ($1 = 0.6506 pounds) (Reporting By Mamidipudi Soumithri and Devika Krishna Kumar in Bengaluru; Editing by Robin Paxton)