Terms of the transfer for the controversial striker serving a biting ban have not yet been revealed by Barcelona.
Liverpool are eyeing Barcelona striker Sanchez as a good alternative to replace Uruguay's Suarez, who will move to Barcelona.
Croatia international defender Dejan Lovren wants to leave Southampton and complete a move to Liverpool, British media reported on Sunday.
Barcelona officials will meet their Liverpool counterparts in London on Wednesday to open negotiations on a possible deal for disgraced Anfield striker Luis Suarez, according to British media reports.
Lallana, Southampton's captain, will rejoin former club and country team mate Rickie Lambert, who also moved to Liverpool.
Manchester City begin the defence of their English Premier League title away to Newcastle then face Liverpool at home.
English Premier League clubs earned a record $4.23 billion in revenue in the 2012-13 season to lead the "big five" leagues in the world.
The 20-year-old had a big part in Leverkusen's fourth-place finish last season in the Bundesliga, scoring three goals in 29 league appearances.
Rickie Lambert has joined Liverpool from Southampton for a reported fee of 4 million pounds ($6.7 million), strengthening the team's attacking options.
Liverpool finished second in the league standings, two points behind Manchester City, following an unexpected challenge for the title.
Luis Suarez is urging his Uruguayan teammates to learn from the fallout of Liverpool's season with the World Cup looming.