The Paris Saint-Germain forward has resumed training as he continues his return from foot surgery, having sustained a broken metatarsal in February.
"Physically I'm okay, my foot is fine", he admitted.
The 20-strong squad will meet again Sunday morning at the Brazilian football confederation headquarters in a visit to their museum.
Speaking before arriving in London, Neymar said: "I'm not yet at 100 per cent".
"Neymar's shown that he's world class", said Asensio. I am adapting to a few things. That will come with time. "Nothing can stop me from doing so", Neymar added.More news: This Is Why Kim Kardashian Visited The White House Yesterday
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The 26-year-old is expected to feature when Brazil travel to the north of England to Liverpool's Anfield stadium for a friendly match with Croatia on June 3rd.
"So, every day we talk because I always go and challenge him and each day he is better, faster and it is more and more hard to block him".
"We hope he'll be 100% ready or as ready as is possible".
Neymar only signed for PSG last summer when he became the world's most expensive footballer of all time when he left Barcelona for the French capital for £198m.
Since the Brazilian star moved to France past year from Barcelona, he has been a target for Real Madrid who want to bring him back to the La Liga.
Let me remind you that in the group stage of the upcoming world championship, starting June 14, the team of Titus will play with the teams of Switzerland, Costa Rica and Serbia.