Nokia on Monday said it had agreed to acquire Boston-based mobile advertising start-up Enpocket, in a move analysts said could put considerable pressure on wireless carriers.

The deal also reflects the Finnish handset maker’s effort to transform itself into a software and services company. Financial terms were not disclosed.

Enpocket displays advertisements on cell phones in various formats, including banner ads, video clips and text messages. It works very closely with carriers such as Sprint Nextel and Vodafone, combining operators’ customer data with real time information, such as a subscriber’s location and key words searched, to place ads that generate higher response rates.

"Enpocket is a good catch for Nokia,” commented Eden Zoller, principal analyst at London based management consultancy Ovum. “It is a well established mobile advertising specialist and one of the stronger players in an increasingly competitive, consolidating market,” she said.

Bena Roberts, founder and senior analyst at BKI Media, a UK-based mobile media analysis company, said the acquisition will put Nokia at both ends of the carriers’ value chain. The Finnish group already supplies devices that subscribers use to access carrier networks and it would also be in a position to deliver advertisers to the network – a very important new source of revenue for wireless operators.

“If I were an operator I would be scared,” she said. “It’s very frightening to think that a mobile manufacturer has that much value in the chain.”

The Enpocket deal follows Nokia’s announcement earlier this month that it intends to shift its emphasis towards software and services. Nokia described the move as “an important element in monetizing those services for our customers and partners.”

 “This will definitely put them in a more consumer facing position,” said Ian Maude, Internet advertising analyst at London-based telecommunications and media consultancy Enders Analysis.

Enpocket is backed by BlueRun Ventures, GrandBanks Capital, Dolphin Equity Partners, Brú Venture Capital.