Chambers needs to run 10.21 secs to have a chance of reaching Beijing
Dwain Chambers missed out on the Olympic 100m qualifying time on his British comeback on Sunday.
Chambers clocked 10.28 seconds in Birmingham, 0.07 secs outside the official 'A' standard qualifying time.
Later he revealed he will not rush into an appeal against his lifetime Olympic ban by the British Olympic Association (BOA) following his two-year drugs ban.
Chambers said: "We're still going through proceedings. When we are ready we will take the necessary steps."
The 30-year-old ran 10.26 secs in his first race over 100m for almost two years on Wednesday in Greece.
That time was already good enough to win him a place at the British Olympic trials in Birmingham on 11 July.
It's important that the public support me and I have been very encouraged by that
But the sprinter, who won a silver medal in the 60m at the World Indoor Championships in March, needs to clock 10.21 secs if he is to pursue his hopes of overturning his ban and representing Britain in Beijing.
Fellow British sprinters Tyrone Edgar, Harry Aikines-Aryeetey and Marlon Devonish have all already achieved that time this season.
Last week, Chambers said he expected his solicitors to be serving legal proceedings against the BOA before the end of this week.
But Chambers sounded more cautious about the process at Alexander Stadium, where he was competing for his club Belgrave Harriers in the British League.
"It's a bit quiet at the moment, they [his solicitors] are doing work but are choosing to keep me out of everything," said Chambers.
"They are briefing me now and again, but they want me to concentrate on my job which is what I'm doing. It will happen at the right time."
Even if his legal challenge succeeds, Chambers, who tested positive for the steroid THG in 2003, is likely to face further opposition.
London 2012 chief Lord Coe has already called Chambers' challenge "damaging to the sport", while his former manager John Regis has said he should not be allowed to compete.
UK Athletics was reluctant to select Chambers for the World Indoors but their first-past-the-post selection policy meant they had no choice but to send him to Valencia.
But Chambers believes his two-year ban from athletics has served as punishment enough.
"What has happened has happened and I can't change it now," he said.
"For me it's important that the public support me and I have been very encouraged by that."