Blair, who earlier testified by video link-up to the US Iraq Study Group probing possible new strategies in the US-occupied nation, offered Iran a new "partnership" on Monday if it satisfied certain conditions.
President George W. Bush's spokesman Tony Snow told AFP interpretations that Blair's remarks signalled cracks between Downing Street and the White House, were overblown.
"You have mischaracterized his position," Snow said. "Read his speech, and you'll see there is no difference between the governments."
Blair's remarks in a major foreign policy address on Monday came on the same day that Bush signalled there would be no softening of the US line towards Syria and Iran, despite a flurry of calls to engage the two powers on Iraq.
As the impact of Blair's remarks sunk in, the White House issued a fact sheet comparing coverage of his speech from London and Washington-based reporters in the New York Times and Washington Post.
London-based reporters for the two papers wrote that Blair offered no dramatic new policy proposals, the fact sheet said.
But their counterparts on the same papers in the United States saw Blair's speech as a shift in policy on Iraq, the fact sheet said, stating : "Prime Minister Blair's Policy Is Not New And Is Similar To President Bush's Policy."
In his speech on Tuesday, Blair said, the West should "offer Iran a clear strategic choice: they help the Middle East peace process not hinder it; they stop supporting terrorism in Lebanon or Iraq; they abide by, not flout, their international obligations.
"In that case, a new partnership is possible. Or alternatively they face the consequences of not doing so: isolation," he said.
A Downing Street spokeswoman told AFP that in the videoconference on Tuesday Blair also called for Iran and Syria to be presented with a "strategic choice."

Copyright AFP (Agence France-Presse), 2006