A group of online travel firms urged the US authorities on Tuesday to block Google's purchase of flight information company ITA Software, saying it would give the Internet titan too much control over the lucrative sector.

"Acquiring ITA Software would give Google control over the software that powers most of its closest rivals in travel search and could enable Google to manipulate and dominate the online air travel marketplace," they said.

"The end result could be higher travel prices, fewer travel choices for consumers and businesses, and less innovation in online travel search," the coalition of travel sites and technology companies said in a statement.

Members of the "FairSearch.org" coalition include Expedia and its brands Expedia.com, Hotwire and TripAdvisor, Farelogix Inc., Kayak and its brand SideStep, and Sabre Holdings and its brand Travelocity.

The group launched a website presenting their case at FairSearch.org.

Google announced in July it was buying ITA Software, which powers many of the Web's most popular travel sites, for 700 million dollars in cash.

"We founded Kayak to give travel consumers access to more choices and lower prices, but this deal could result in just the opposite," Kayak co-founder and chief executive Steve Hafner said.

Expedia chief executive Dara Khosrowshahi said "combining Google and ITA -- the dominant providers of Web search and flight search technology, respectively -- raises some serious concerns for travelers and the online travel industry."

Thomas Barnett, a former US assistant attorney general who now serves as counsel to Expedia, said that the Justice Department needs to "thoroughly investigate the proposed acquisition."

ITA, a 500-person firm based in Cambridge, Massachusetts, specializes in organizing airline data, including flight times, availability and prices.

Its QPX flight data organization tool uses algorithms to combine flight information from airlines, including pricing and availability, to create a searchable database.

QPX software is used by online travel agencies and airlines including Alaska Airlines, American Airlines, Continental Airlines, Southwest Airlines, United Airlines, US Airways, Virgin Atlantic Airways and others.

Microsoft's Bing, Kayak, Orbitz and TripAdvisor are among ITA's customers.

Andrew Silverman, a Google senior product manager, dismissed the claims made by FairSearch.org saying "our reason for making this acquisition is simple: ITA will help us provide better results for our users."

"It's disappointing that a number of travel companies have today announced their concerns about the deal," Silverman said in a blog post.

"ITA and Google are not competitors so there will not be less choice for consumers," he said, adding that the three most popular travel sites in the United States -- Expedia, Priceline and Travelocity -- use data provided by ITA's competitors.

Silverman noted that Google does not plan to sell airline tickets directly and reiterated that it will honor all of ITA's existing agreements.