SEOUL/SAN FRANCISCO (Reuters) -Samsung Electronics on Wednesday unveiled its newest Galaxy S25 smartphones, powered by Qualcomm's chips and Google's artificial-intelligence model, hoping its upgraded AI features can reinvigorate sales and fend off Apple and Chinese rivals.

Samsung also previewed a thinner version of the flagship models at the end of an event in California, aiming to launch the Galaxy S25 Edge in the first half of this year ahead of Apple's anticipated rollout of its slimmer iPhone.

Samsung was faster than Apple in launching an AI-powered smartphone but failed to regain its crown in the global smartphone market last year, squeezed by competition with the U.S. rival in the premium market and with Chinese firms in the lower-end segment.

"We are one step ahead of the industry in terms of offering AI features. I believe we are going in the right direction," Park Ji-sun, the executive vice president who leads Samsung's Language AI team, told Reuters.

Samsung kept the prices of its Galaxy S25 series unchanged at between $799 and $1,299.

The new Galaxy S25 uses Gemini offered by Alphabet's Google as its default AI engine, and features Samsung's upgraded in-house voice assistant, Bixby, Park said.

The two tools complement each other, and Bixby plays a key role at Samsung, whose products span mobile phones to TVs and home appliances, he said. 

Thomas Husson, an analyst at Forrester, said that differentiating Bixby would be a challenge for Samsung. 

"I don't think there is really a killer application today that you know would convince them (consumers), 'OK, I'm going to buy this one because it's an AI smartphone,'" he said.

Husson added, however, that AI features could create a halo effect around the Samsung brand.

The Galaxy S25 will offer a more personalized AI experience. For example, its "Now Brief" service - which makes recommendations to users based on personalised data that is stored and processed on the phone for privacy reasons - will display a suite of customised items such as calendars, news and bedroom air temperature and carbon dioxide levels, Park said. 

The phone will be able to carry out multiple tasks with a single command, such as finding upcoming sporting events and then adding them to users' calendars.

Samsung shares were down 1.1%, lagging the wider market's 0.4% loss.

Samsung used Qualcomm's Snapdragon 8 Elite Mobile Platform for the entire Galaxy S25 lineup, ditching its own mobile chip Exynos, a major change of strategy for a company that previously used both to have more bargaining power with suppliers.

Using a Qualcomm chip is a setback to the South Korean firm's chip business, which counts its mobile division as one of its major customers.

Samsung did not say why it decided not to use its own chips in the new model.

A person familiar with the matter said Samsung is looking to use the Exynos chip in its foldable phones to be launched later this year.

"The Galaxy S25 series' sale is important at a time when Samsung's foldable phone sales have been stagnating in the face of challenges from Chinese companies," Lim Su-jeong, associate director at research firm Counterpoint, said.

Samsung's preliminary fourth-quarter profit, released earlier this month, missed estimates by a large margin due to chip development costs and rising competition in the smartphone market.