The gifted 23-year-old attacking midfielder is moving to Anfield from Germany's Hoffenheim, where he played since 2010, scoring 47 goals in 151 appearances.
Arsenal took the race to the final day last season and are strongly tipped to end Manchester City's dominance this time.
Unsettled striker Carlos Tevez returned to Manchester City on Monday and the English city he had sworn he would never return to.
Brazil will play Argentina in two friendlies next month, one in each country, with teams picked from the domestic leagues, the Brazilian Football Confederation (CBF) said on Wednesday.
It is a mistake to compare Argentina with Barcelona as the Spanish club have been working as a unit for a lot longer, Lionel Messi said on Thursday.
Substitute Fred struck in a last-minute equaliser to give holders Brazil a 2-2 draw with Paraguay before unfancied Venezuela upset Ecuador 1-0 to go top of Group B at the Copa America on Saturday.
Gonzalo Higuain is training for a similar role to Lionel Messi's in the Argentina team in preparation for matches when the Barcelona forward is not playing, coach Sergio Batista said on Tuesday.
Argentina captain Lionel Messi said defending champions France and Brazil are the favourites to win the World Cup in Qatar as they have a core group of players who have played together for a long time.
Carlos Tevez has been included in the squad for the first time in three years for next month's friendlies in England against Croatia and Portugal.
Argentina lifted the gloom from a poor Copa America by routing Chile 4-1 in their opening 2014 World Cup qualifier on Friday, while Uruguay also scored four to get their campaign off to a good start.
Holders Brazil and their Group B rivals breathed life into the Copa America in two six-goal thrillers as they qualified for the quarter-finals with Venezuela and Paraguay on Wednesday.
Argentina's hopes of reaching the 2010 finals in South Africa could be severely limited this weekend, should the results of the South American World Cup qualifiers go to form. Diego Maradona's Argentina face Dunga's South American group leaders Brazil (27 points), who added the Confederations Cup in late June to their 2007 Copa America title.
Lionel Messi at last came into his own at the Copa America as Argentina beat a defensive Costa Rica 3-0 with two goals from Sergio Aguero to secure second place in Group A on Monday.
Striker Radamel Falcao scored twice as Colombia beat Bolivia 2-0 to win Group A at the Copa America on Sunday.
Peru edged Mexico 1-0 at the Copa America on Friday to move level on points at the top of Group C with Chile, who had earlier come from behind to draw 1-1 with Uruguay.
Argentina's hopes of making the quarter-finals of Copa America suffered a huge setback when they were held to a goalless draw, this time by Colombia, on Wednesday.
Lionel Messi is Argentina's centre forward, coach Sergio Batista said on Monday as he closed the Copa America door to Carlos Tevez.
Teenage strike Neymar scored twice on his third appearance for Brazil as the South Americans outclassed Scotland 2-0 in a friendly played in something of a carnival atmosphere at Arsenal's Emirates Stadium on Sunday.
"Our team fulfils our dreams!" and "Where is Messi? We beat him!", the green-clad Saudis chanted over and over in the Lusail Stadium, on their feet and greeting every clearance, including one headed off the goal line with a deafening roar.
Barcelona must considerably reduce their wage bill in order to keep Lionel Messi, La Liga chief Javier Tebas said on Thursday, adding that the club would not be shown any leniency when it comes to obeying the league's strict financial control rules.
Brazil continue to top the rankings, which has India placed at 151.
Brazil rounded off a very good pre-World Cup year with a lacklustre 2-0 win over Oman in a friendly on Tuesday to take their tally to 14 victories in 17 matches.
Shakhtar Donetsk coach Mircea Lucescu admitted he went against UEFA's wishes in fielding midfielder Fred in Tuesday's Champions League qualifier despite being aware of a possible doping violation hanging over the Brazilian international.
Messi's World Cup chase takes centre stage in quarter-final clash
Brazilian police said on Tuesday they had recommended no rape charges against soccer star Neymar, after a woman he met online said he flew her to Paris and assaulted her in a hotel there.
The Argentine Football Association (AFA) will appeal what it says is FIFA's decision to force Brazil and Argentina to replay their World Cup qualifier, which was cancelled after five minutes due to a breach of COVID-19 quarantine rules.
Hundreds of Argentines protested in the pouring rain on Saturday, demanding that soccer star Lionel Messi return to Argentina's national team after he unexpectedly quit following a loss in the regional Copa America final.
Brazil struggled to an uninspiring goalless draw away to Colombia in their opening match of the World Cup qualifiers.
The World champions will be banking on their 'Magic Quartet' to win them the record sixth title
The European champions moved to No. 14 in FIFA's latest rankings announced on Wednesday.
Brazil climbed up from third place after beating Argentina 3-0 in the Copa America final on Sunday.
Dunga's appointment as Brazil coach after last year's World Cup was greeted with scepticism by many because he had no previous experience.
Argentina beat Mexico 3-0 to set up a meeting with Brazil in the Copa America final.
Aimar and Tevez add to Crespo's brace to give the South Americans a 4-1 win.
Real Madrid will take the Spanish championship for the first time in four years if they beat mid-table Real Mallorca at home on Sunday.
Brazil have added Real Madrid striker Julio Baptista to their Copa America squad after midfielder Ze Roberto quit international football.
Brazil's preliminary Copa America squad includes Germany's Footballer of the Year Diego of Werder Bremen and Real Madrid forward Robinho.
Factbox on the Brazilian, who was named European Footballer of the Year.
No amount of preparation is enough to snuff out the threat of Argentina's "assassin" Lionel Messi, Panama coach Hernan Dario Gomez said ahead of Friday's Copa America clash between the teams. Messi was an unused substitute in Argentina's 2-1 win over holders Chile in their opening Group D match in Santa Clara, California on Monday after a back injury but will reappear when they face Panama in Chicago. "Leo trained normally, he will play," coach Gerardo Martino told a news conference on Thursday. Both sides have three points after Panama marked their first appearance in the world's oldest international tournament with a surprise 2-1 win over Bolivia, who face Chile in Foxborough on Friday.