Rupert Cornwell: The clock's ticking... first impressions count

Every US president is judged by his first 100 days. But those of Barack Obama are almost certain to be the most momentous and transformative since Franklin Roosevelt took power at the depths of the Great Depression.

Every condition is in place for a blizzard of action – in Congress, on the diplomatic front, and through executive decisions by the White House which will send powerful signals of the direction in which he intends to take the country.

First, Americans are aching for change, visible in Mr Obama's record high approval rating for an incoming president of 75 per cent – a figure underlining how goodwill towards him, and the desire that he succeed, crosses party lines. It also gives him an immense authority. A president is at his most powerful in the early stages of his term; never has that been truer than now.

Second, thanks to an exceptionally well-organised transition, the new administration is well placed to hit the ground running. Third and most important, Mr Obama has no choice but to move fast.

The expected initiatives fall into three broad categories. The easiest, and likely to be among the quickest, are straightforward but highly symbolic decisions that show the Bush era is over. These moves, which aides refer to as "low-hanging fruit," will include the order to close Guantanamo Bay prison within 12 months as he signalled yesterday.

Mr Obama may also issue an early order lifting Mr Bush's restrictions on federal aid for stem cell research. He may also take steps to ease curbs on travel to Cuba. That would signal the days are finally numbered for the 50-year-old US embargo that has failed to bring down the Castro regime and is opposed by almost every country on earth.

The second category consists of the steps Mr Obama simply has to take – to revive the economy and prevent the collapse of the US financial system. Even before taking office, he had lobbied successfully for Congress to release the second tranche of the $700bn bank bailout package.

Within a few weeks, lawmakers are likely to pass a stimulus package of tax cuts and increased federal spending worth $800bn or more, while Mr Obama's economic team will have to come up with further aid for the distressed banking system. The aid will almost certainly be linked with help for home-owners facing foreclosure.

The third category is less specific but perhaps the most far-reaching and aimed at making good what he referred to in his inaugural address as "our collective failure to make hard choices, and prepare the nation for a new age." Under that heading come the biggest issues of all: America's failure to live within its means, the curbing of runaway entitlement programmes in general and the overdue repair of a bloated, inefficient and hugely expensive healthcare system.

These may not be achieved in 100 days, or even 1,000 days but speed here too is of the essence. The country wants to be told the truth and is ready to make sacrifices. Right now, the "bully pulpit" potential of the presidency is at its zenith.

In short, it's going to be an action-packed 100 days, even without a major foreign crisis, in the Middle East or over Iran's nuclear programme, say, to scramble everything.