MPs were on the alert for a second recall of the Westminster Parliament last night amid the first signs of pressure on the British political consensus on the international crisis.
The Conservative leader, Mr Iain Duncan Smith, will today renew his strong support for the Prime Minister, Mr Tony Blair, in backing the imminent American action against those believed responsible for the terrorist atrocities in Washington and New York.
That follows yesterday's more conditional pledge of support from the Liberal Democrat leader, Mr Charles Kennedy, who said Britain should stand "shoulder to shoulder" with the US while being prepared to act as America's "candid friend".
Echoing concerns on the left of the Labour Party, Mr Kennedy told the Liberal Democrat conference in Bournemouth that "a proportionate response" to the US terror attacks was "not just about military measures" but "about civil liberties" as well.
Amid signs of growing alarm about the scale of new emergency laws presently being considered by the government, Mr Kennedy warned his party of "difficult dilemmas ahead" in striking the balance between liberty and the threat posed to it by terrorism.
Distancing himself from the rhetoric already deployed by Mr Blair and President Bush, Mr Kennedy told his delegates: "'War' is not the word for it, nor is 'crusade'. Resolve is." While making common cause with Mr Blair that there be "no capitulation to the terrorist", Mr Kennedy said: "As America's candid friend we are able to say there are no blank cheques . . ." And he suggested full British involvement in all planning and risk assessment in respect of her armed forces should be a condition of UK support for military action.
With the time for that action drawing ever closer, Mr Blair spent yesterday cementing his domestic support - briefing the members of key Commons Committees and the Tory leader - while Mr Jack Straw continued the government's coalition-building with his ground-breaking visit to Iran.
Downing Street played down controversy sparked by the Foreign Secretary's letter published in the Iranian press, criticised by the Israelis, insisting London had wanted to see the Middle East peace process re-invigorated prior to the events of September 11th.
"It's not a case of either, or," said a spokesman, referring to the combined commitment to continuing diplomacy and the need to frame the right military response to the American attacks.
With some reports suggesting Mr Blair might recall MPs as early as Friday, official sources continued to indicate that parliament would most likely be reconvened once military action was under way. There are also strong indications that next week's planned Labour Party conference will be significantly curtailed because of the unfolding crisis.
While refraining from any criticism of Mr Blair in his speech tonight, Mr Duncan Smith is expected to press for an assault on terrorism "on all its fronts" and not just in so-called "rogue states". The Tory leader will refer to the fund-raising activities of republican terrorists, and speak of the need to tackle "the mafia subculture" associated with terrorism at home as well as abroad.
This intervention comes after Mr David Trimble's strongest-ever attack on Mr Blair yesterday, when he asserted: "One cannot credibly fight terrorism abroad while temporising with it at home."