Iraq's vice-president claims Tony Blair was "brainwashed" by President Bush into not setting a timetable for troop withdrawal from Iraq.
Mr Hashemi met Mr Blair around three months ago
Tareq al-Hashemi suggested Mr Blair had supported his idea of announcing a timetable, but then changed his mind after talking to Mr Bush.
The two leaders discussed the issue about three months ago, after which the PM was to raise the issue with Mr Bush.
The US president has so far refused to set a timetable for troop withdrawals.
Speaking in New York, Mr Hashemi said Mr Blair had been convinced by his proposal for a timetable for withdrawal.
He told the Council on Foreign Relations: "It is quite unfortunate that your president made a sort of blackmail out of Mr Blair."
He later told the BBC: "After a lengthy discussion with [Tony Blair]...I got the impression that he was becoming convinced about my team and he promised to take up this matter with President Bush within a couple of days.
"But I was observing the joint press conference that he made with President Bush after his visit and I saw him talking about something quite different, which gave me an impression that he raised this subject with President Bush and eventually he just changed his mind."
"I think he discovered that Mr Bush is still adamant that he's not going to declare some sort of timetable for withdrawal to avoid passing wrong messages to terrorism," he said.
Mr Hashemi, head of the Iraqi Islamic Party and one of the country's most prominent Sunni Muslims, was elected vice-president in April.
Days later his sister Meysoun, head of the women's affairs department for the party, was killed in a drive-by shooting in the capital Baghdad.
The attack followed the killing of one of Mr Hashemi's brothers earlier that month.