Wales face England at Twickenham on Saturday 6 August before hosting the old enemy in the return fixture at the Millennium Stadium seven days later.
Argentina provide the final opposition on home soil on Saturday 20 August, before a 30-man Wales squad for the 2011 RWC in New Zealand is named two days later.
Ospreys flanker Jonathan Thomas, Sale Sharks back row Andy Powell, Blues prop Scott Andrews and Scarlets hooker Ken Owens, who all took part in Wales' first pre-RWC training camp in Poland, but not the second, have all returned to put themselves in contention for selection against England.
The rest of the 35-man squad, which made the second trip to Poland, including Melbourne Rebels flanker Gareth Delve who joined up late, have all been retained - with the exception of Rob McCusker who has struggled with back problems.
Gatland and his coaches will name the side to face England, based on this squad, but players who remain outside of it may still be involved in future warm-up matches and could still be a part of the 2011 RWC campaign.
"The team to face England at Twickenham will be selected from this training squad," said Gatland.
"We have established a nucleus of players who will form our RWC squad based on their performances in training over recent weeks, but it is now time to translate those efforts onto the field. The players have worked hard, but places in that final world cup squad are still very much up for grabs and a lot will depend on what we see over the course of these next three games.
"We have not shied away from facing the top quality opposition in preparation for this world cup and it doesn't come much tougher than facing the 2003 World Cup winners and 2007 finalists on their home patch. The warm-up fixtures will be tough, but we are in a really tough group at the world cup and replicating those conditions can, ultimately, only be of benefit to us."
Fans can watch the squad in action as soon as next Tuesday, 2nd August, when Millennium Stadium doors will be thrown open for a 'free to enter' training session from 2.30pm - for more information and to register to attend visit www.wru.co.uk/watchwales4free.
"Tickets for Wales' clash with England at the Millennium Stadium are priced £30 and tickets to the Wales versus Argentina game (both kick-offs 2.30pm), which are on a 'buy one get one free' promotion, are priced at £25 and all are available online at www.wru.co.uk/tickets or by calling the ticket hotlines 08442 777 888 or 02920 230130 or at local Tesco stores."
RWC 2011 Preliminary 39-Man Squad:
Scott Andrews, Gethin Jenkins (Blues), Lloyd Burns (Dragons), Huw Bennett, Ryan Bevington, Adam Jones, Paul James (Ospreys), Ken Owens, Matthew Rees (Scarlets), Craig Mitchell (Exeter Chiefs).
Bradley Davies, Sam Warburton, Martyn Williams (Blues), Luke Charteris, Danny Lydiate, Toby Faletau (Dragons), Ryan Jones, Alun Wyn Jones, Jonathan Thomas, Justin Tipuric (Ospreys), Josh Turnbull, (Scarlets), Gareth Delve (Melbourne Rebels), Andy Powell (Sale Sharks).
Michael Phillips (Bayonne), Lloyd Williams (Blues), Tavis Knoyle (Scarlets)
Jamie Roberts (Blues), James Hook (Perpignan) Jonathan Davies, Stephen Jones, Rhys Priestland, Scott Williams (Scarlets) Gavin Henson (unattached)
Leigh Halfpenny (Blues), Lee Byrne (Clermont Auvergne), Aled Brew (Dragons), Shane Williams (Ospreys), George North, Morgan Stoddart (Scarlets).