Gerrard had been undergoing rehabilitation from groin surgery that ended his season in mid-March but manager Kenny Dalglish had expected him to be back for the start of the new campaign.
However, a statement on the club's website on Saturday revealed he will not be available until September after being hospitalised for treatment, leaving him struggling to be ready for England's trip to Bulgaria on September 2 and visit of Wales four days later.
"Steven Gerrard today began a course of antibiotic treatment for an infection related to an ongoing groin problem," it said.
"He is expected to remain in hospital for several days while the precautionary procedure is completed.
"The player will then return to Melwood to continue his rehabilitation programme and is expected to be available for selection in September."
The England midfielder, who sat out the club's brief tour of the Far East this summer, will therefore miss Liverpool's Barclays Premier League fixtures against Sunderland, Arsenal and Bolton, with the trip to Stoke on September 10 a possible target for his return.
Gerrard, who last played for England in November last year, was already likely to miss the international friendly with Holland on August 10.
While his absence will be a blow to both Dalglish and England boss Fabio Capello, the Reds manager has cover in midfield having recruited heavily this summer while the emergence of Jack Wilshere has added depth to the national side's ranks.
One man likely to benefit from Gerrard's injury will be summer signing Charlie Adam, who is desperate for opportunities to impress after arriving from Blackpool.
The Scotland international told liverpoolfc.tv: "I can't wait to get started and hopefully this will be a successful period in my career and in the club's history.
"At the end of the day you get judged on trophies and as a footballer you want to win as many as you can. This club has had a lot of success over the years, so let's get back to doing that.
"Liverpool have many other talented midfielders, the likes of Steven Gerrard, Lucas Leiva, Raul Meireles and Jordan Henderson.
"I think the competition for places will be good for the club. I thrive on that type of challenge and I'm sure the other lads will as well.
"I want to learn and there are some of the best players in the world at this club, so if I can learn from them I am going to improve as a player. That is my aim.
"I see this as the perfect development for me to come here, play with such wonderful players and hopefully help the team to win trophies, because that's the most important thing."
Liverpool's disappointment over Gerrard will be partially offset by the news Jose Reina is ready to return after hernia surgery.
The goalkeeper has not featured during pre-season after an operation but is set to face Valerenga on Monday with the season opener against Sunderland a fortnight away.
"The target is to play in Valerenga, and then after Valencia there is one more week and that should be good enough to get that fitness," said the Spain international.