Blair wanted to increase the period from 14 to 90 days. But in November 2005 he suffered his first parliamentary defeat since coming to office in 1997 when MPs instead backed a compromise extension to 28 days.
The prime minister said he would bring forward proposals for possible new counter-terrorism legislation before the end of the year but added it was too early to say whether it would be put to a vote.
"We will bring back, I think before Christmas, proposals that will be based on an analysis now of what has gone on in the past few months and how we make sure we have the most effective laws to deal with the terrorist threat we face.
"The issue to do with the number of days of detention will be part of that.
"We will look at that, depending on the evidence," he said, during a webcast on his official website.
Blair's comments come the day after Queen Elizabeth II's speech at the annual state opening of parliament, setting out the government's legislative programme for the coming year.
This focused on security but did not contain specific reference to extending the period of detention for terrorism suspects.
His comments attracted a dismayed response from human rights group Liberty, whose director Shami Chakrabarti said 90-day detention was "our nightmare but a terrorist recruiter's dream".
The issue was revived last weekend when Britain's most senior policeman, Ian Blair, called for tougher anti-terrorism measures, including extended custody periods and was backed by Blair's deputy Gordon Brown.
Home Secretary John Reid on Wednesday refused to rule out taking the matter back to lawmakers.

Copyright AFP (Agence France-Presse), 2006