(Reuters) -Alphabet shares jumped 4% on Thursday, rising for a second straight day, as investors cheered the Google parent's artificial intelligence updates including the rolling out of "AI Mode" to all its U.S. users.

A $249.99-a-month subscription for its AI power users, teased at its annual developer conference, also allayed concerns over funding the huge costs of the company's AI development.

After the conference, "we are incrementally confident that Google can deliver continued search growth while ramping monetization suggesting improving execution," Citi analyst Ronald Josey wrote in a note.

CEO Sundar Pichai said the rise of generative AI was not at the full expense of online search amid concerns about a behavioral change where users were turning to AI chatbots from search engines.

In a major update, the company signaled that customers across the U.S. now can switch Google Search into "AI Mode."

A Google search team executive also said using AI to answer tougher questions could open up new ways to show more relevant and useful ads. Ads make up the majority of Google's revenue.

"We believe monetization of AI Mode is likely to 'soon' follow the U.S. launch," Josey said.

Class C shares of Alphabet were up 4% at 175.27, trading at levels last seen three months ago. The stock is down about 7% so far this year.

(Reporting by Medha Singh in Bengaluru; Editing by Sriraj Kalluvila)