The day before the September 11 attacks, the Bush administration agreed on a plan to oust the Taliban regime in Afghanistan by force if it refused to hand over Osama bin Laden, according to a report by a bipartisan commission of inquiry.

The report pointed out that agreement on the plan, which involved a steady escalation of pressure over three years, had been repeatedly put off by the Clinton and Bush administrations, despite the repeated failure of attempts to use diplomatic and economic pressure.

The revelation emerged at the beginning of the commission's hearings this week on the country's failure to prevent the attacks, in which the top officials from both administrations came under scrutiny.

The hearings followed two days of uproar in Washington over allegations from a former White House counter-terrorism tsar, Richard Clarke, that the Bush administration's ideological obsession with Iraq had hindered the momentum of the struggle with al-Qaida in the months before the attack. Mr Clarke claimed that the plan to increase the pressure on the Taliban was inherited from the Clinton administration.

However, in testimony to the commission, the secretary of state, Colin Powell, said the September 10 meeting of top White House officials, to agree the strategy towards the Taliban, demonstrated a new determination to deal with al-Qaida.

The report drawn up by the commission's staff said: "From the spring of 1997 to September 2001, the US government tried to persuade the Taliban to expel Bin Laden to a country where he could face justice. The efforts employed inducements, warnings and sanctions. All these efforts failed."

At a meeting of the Bush administration's top national security officials on September 10, a three-phase strategy was agreed.

The Taliban would be presented with a final ultimatum to hand over Bin Laden. Failing that, covert military aid would be channelled to anti-Taliban groups. If both those options failed, "the deputies agreed that the United States would seek to overthrow the Taliban regime through more direct action."

However, the three-step process would have taken up to three years, and did not represent an immediate attack plan.

The next day, hijacked planes destroyed the World Trade Centre and hit the Pentagon, triggering the launch of an anti-Taliban offensive in October and the Taliban's fall a month later.

Yesterday, it was the turn of Clinton administration veterans to face questioning on why they had failed to take more aggressive action against al-Qaida in the wake of the 1998 bombings of US embassies in Africa and the 2000 attack on the American destroyer USS Cole.

The former officials defended their record but also revealed splits in the Clinton administration on how to respond to the attacks. Madeleine Albright, the former secretary of state, directed blame at the Clinton-era defence department under William Cohen for not agreeing to use special forces to hunt down al-Qaida in the Afghan mountains.

"I'm personally not satisfied we were able to get the right answers out of the Pentagon," she said. Mrs Albright said she had repeatedly pressed for alternative military measures other than the cruise missile strikes on suspected al-Qaida bases that were tried after the embassy bombings. She said the Pentagon told her that special forces units would either be too small to protect themselves or too large to be covert.

Testifying later, Mr Cohen said that more than 13,000 coalition troops in Afghanistan had failed to find Bin Laden, so questioned what success a small special forces unit might have had.

The commission heard that after the African embassy bombings in Kenya and Tanzania, the Clinton administration presented an ultimatum to the Taliban warning it would bear the consequences if there were another al-Qaida attack.

The commission members, drawn from the ranks of retired officials and politicians from both parties, repeatedly asked why that threat was not delivered after the 2000 attack on the USS Cole.

Mrs Albright said that by the time the Clinton administration left office in January 2001 there was still no "definitive proof" of al-Qaida involvement in the suicide attack off the Yemeni coast. John Lehman, a navy secretary in the Reagan administration and one of the commissioners, alleged that the CIA was already convinced of al-Qaida's responsibility by December, but Mrs Albright said that finding was not passed on to the political leadership.

Asked the same question, Mr Powell said that before the September 11 attacks, there was no consensus in the Bush administration on how far to go against al-Qaida and the Taliban.

"We did not take into account during that period the kind of actions we were prepared to follow after 9/11," he told the inquiry. "It was not clear how to get at al-Qaida in a way to destroy al-Qaida, and we were not prepared, before 9/11, to take down the Taliban."

Mr Powell vigorously rejected the claim, made by Mr Clarke in a White House memoir published on Monday, that the Bush administration had failed to take the terrorist threat seriously,

"President Bush and his entire national security team understood that terrorism had to be among our highest priorities, and it was," he said. Mr Powell said holding more meetings on the issue would not have accelerated efforts to arm a US hi-tech surveillance drone, the Predator, with missiles so that it could track and, if necessary, attack Bin Laden in Afghanistan - one of the measures urged by Mr Clarke.

The armed Predator was only ready by autumn 2001.

Mr Powell and his deputy, Richard Armitage, also objected to suggestions that the US should have acted earlier to arm the anti-Taliban Northern Alliance. They said the Northern Alliance was in no position to pose a serious military threat to Kabul, and was implicated in drug dealing and human rights abuses. Only after September 11 2001, they argued, when US special forces soldiers were sent to collaborate with the Northern Alliance, was it feasible to increase direct military aid.

The main players, past and present

Madeleine Albright, secretary of state 1997-2001

Under pressure yesterday for having been too soft on the Saudis and the Taliban. She blamed William Cohen and the Pentagon for failing to send special forces after al-Qaida.

Colin Powell, secretary of state since 2001

On the defensive over the Bush administration's failure to act faster against al-Qaida. He denied that having more meetings on the subject would have been more effective. The Bush White House and the Pentagon are likely to face intense criticism

William Cohen, defence secretary 1997-2001

Dropped in hot water by caution on the use of ground troops. He personified the conservatism of the American defence establishment before September 11

Donald Rumsfeld, defence secretary since 2001

Was more concerned with reorganising armed services and with Star Wars anti-ballistic missile programme than terrorism before September 11. He is alleged to have favoured bombing Iraq in the immediate aftermath because it had more promising targets than Afghanistan