Adam Lallana's hopes of joining Liverpool before the World Cup may rest on informing Southampton he is determined to leave St Mary's, with the two clubs yet to agree a deal for the England midfielder.

The 26-year-old is high on Brendan Rodgers' transfer wish-list for the summer, with the Liverpool manager determined to add proven talent to a squad that will be competing in the Champions League next season. Liverpool have inquired about a £20m deal for the Southampton captain but the south-coast club are believed to value their academy graduate in the region of £25m.

With Roy Hodgson keen to avoid any distractions before England take their World Cup preparations to Miami on 1 June, and Rodgers preferring to complete his main signings early, Lallana may have to leave Southampton in no doubt over his intentions to seal the transfer swiftly. The boyhood Evertonian suggested this week that he was undecided over his future but he is understood to favour a move to Anfield over other interested parties, including Manchester United.

Rodgers would not be drawn on Liverpool's pursuit of Lallana on Tuesday, when he held a lengthy meeting with the club's recruitment team over their preferred targets, but he reiterated that the Premier League runners-up need quality not quantity this summer.

"I don't want to put a figure on how many but I would rather have one or two absolute top players than seven that might not help us," said the Liverpool manager. "It's about the quality. We can't be going into the Champions League this year with doubts about players. We have to be going in knowing what the players' capacity to play is and their capabilities."

Liverpool's defence is in obvious need of strengthening, with a new left-back a priority for Rodgers, although the interest in Lallana demonstrates the manager is also intent on enhancing the attacking threat of a team that scored 101 league goals last season. Real Madrid continue to be linked with a bid for Luis Suárez, as occurred last summer when no offer materialised from the Spanish club, but the striker's declared reason for wanting to leave last year – no Champions League football – has been satisfied at Anfield.

Rodgers' intention is to sign players before the World Cup but he admits he is prepared for all eventualities given the quality he has targeted. "Ideally you would want to get things done beforehand but it is difficult because transfers are so complex, especially if you are doing a big signing," he said. "The World Cup does make it difficult but the club and ourselves have been preparing for quite a few months now so we will try and get the business done as early as we can. I'm sure some of that will get dragged out during the summer, though. You can plan early but sometimes with the madness of football you will find things don't get done until the last 48 hours of the window.

"For me, it's about planning. We have the core of the squad now, that helps. Two years ago, when I came in, I was looking to introduce new ideas but a lot of the players weren't there because of the European Championship. That affected the start of the season. At least this summer we have the principals bedded in place and the players that will come in will be the profile of what we want. It should be better for us this summer."

Rodgers, meanwhile, believes Raheem Sterling can have a major impact at the World Cup providing Roy Hodgson deploys the 19-year-old in positions he has flourished for Liverpool.

"Raheem is an offensive player, a creative player who works hard," the Liverpool manager said. "If he is given the opportunity to play how he can play, whether at the point of a diamond or on the sides, then he could be one of the stars of the World Cup. Let's not forget he is a 19-year-old who has been one of the top players in one of the most competitive leagues in the world.

"He has already shown that he can play in a league that is not just a British league but a league full of world-class, international players. His best games have been against the best teams – Arsenal, United and Manchester City – so he is more than capable. If he continues to have that confidence and play with no fear he could be a really stand-out player if he is asked to play that way. That is key."