Tony Blair's struggle to convince a sceptical public of the need for action against Iraq moved up a gear yesterday when he made his strongest connection yet between Saddam Hussein and al Qaida terrorists.

The Prime Minister told MPs that the Government was aware of links between Osama bin Laden's network and the Iraqi regime, although it was not clear how far they went.

The Foreign Office said that it believed al Qaida operatives had been in Iraq with the "knowledge and acquiescence" of the Baghdad government.

Mr Blair's comments came as he prepared to embark on a hectic round of shuttle diplomacy in an attempt to build support for possible military action.

He echoed a warning by US President Bush early yesterday in his State of the Union address that Iraq could be secretly arming terror groups with weapons of mass destruction.

Mr Bush said America had evidence from intelligence sources, secret communications and suspects currently in captivity that Saddam was involved in "aiding and protecting" al Qaida.

The disclosures appeared to be part of a concerted effort by London and Washington to build support for military action, both among their own publics and the wider international community.

They drew a fierce denial from the Iraqi deputy prime minister Tariq Aziz, who insisted that his country had "no connection" with al Qaida. "I absolutely deny that. And I challenge Bush and his government to present any, any evidence of that," he said.

Speaking at Prime Minister's Questions, Mr Blair acknowledged that they had no evidence linking Iraq to the attacks on the World Trade Centre and the Pentagon, but said that a connection with al Qaida had been established.

But he said: "We do know of links between al Qaida and Iraq. We cannot be sure of the exact extent of those links."

Mr Blair issued an impassioned appeal for national unity, warning that public divisions could undermine demands for Saddam to disarm.

"It is surely better that we combine now as a House, as a country, to put maximum pressure on Saddam because the one thing that would make conflict inevitable is a signal of weakness in our determination to deal with him," he told MPs.

A Foreign Office spokes-man said later: "We do believe that there have been al Qaida operatives in the part of Iraq which is controlled by Baghdad."

British ministers - unlike the Americans - have previously been cautious about publicly linking Iraq to al Qaida, previously talking only of "loose links".

US Secretary of State Colin Powell is due to present America's evidence of Iraq's terrorist links and banned weapons programmes to the United Nations Security Council next Wednesday.

Mr Powell said last night that the evidence would support the findings of the chief UN weapons inspector, Hans Blix, and the head of the International Atomic Energy Agency, Mohamed Elbaradei.

"It will reinforce what Dr Blix and Dr ElBaradei said earlier this week that they are not getting the co-operation they need, that they're being deceived, that they're being misled," he said.

"We will also point out what we believe is the truth with respect to chemical and biological programmes.

" I think you will find it to be a straightforward, sober assessment. Nothing theatrical, but I think we can make the case."

Billy's pal ready for the Gulf

Billy Elliott star Stuart Wells yesterday swapped ballet for bullets and biological weapons training as he helped his regiment prepare for a possible war with Iraq.

While the film's hero, Jamie Bell, found Bafta success as ballet-loving Billy, Stuart turned his back on acting to join the Army.

He enlisted with the Royal Regiment of the Fusiliers, who are due to become some of the first British soldiers to travel to the Gulf.

Stuart, from Wallsend, Tyneside, played Billy's best friend, cross-dressing Michael Caffrey in the film about a boy from the North-East who wins a place at the Royal Ballet School.

He was offered other roles but the 20-year-old said: "I'm not sure why, but acting wasn't for me. I'd had enough."

Stuart, who joined the Army in 2001, has been training on the windswept plains of Celle, Germany.

Asked if he regretted leaving his acting career, he said: "Sometimes, when I'm sitting somewhere cold and wet, but not that often."

Stuart and his younger brother, John, 18, who is in the same company of the regiment, will travel to the Gulf in the next few weeks as part of Britain's lead battle group.