The US maintains military bases in 140 foreign countries (needless to say, there are no foreign military bases on US territory). Thanks to exorbitant military spending more than the combined total of the 32 next most well-armed nations - the US enjoys a unique and coercive global reach, a monopoly which it intends to preserve at all costs, as the current National Security Strategy makes clear. The US claims and exercises a prerogative to topple other regimes and occupy other countries that it denies to all other nation-states. Through the IMF, WTO and World Bank, it shapes the economic destinies of most people on the planet. The fact is that the fate of billions living beyond US borders is determined by decisions made in Washington.

Yet, we are told, this is not an empire. True, the US prefers indirect over direct rule; its domination is exercised, for the most part, through military and commercial alliances, rather than outright conquest. But empires of the past have also used these methods. What really makes the US different is the persistence and in most cases the sincerity of its imperial denial.

Shortly after the invasion of Iraq, Donald Rumsfeld insisted to Aljazeera: "We're not a colonial power. We've never been a colonial power." Colin Powell agreed: "We have never been imperialists. We seek a world in which liberty, prosperity and peace can become the heritage of all peoples." They seemed astonished and offended that anyone could think otherwise.

The litany of disclaimers echoes down the years. Sandy Berger, Clinton's national security advisor, described the US as "the first global power in history that is not an imperial power." Nixon wrote in his memoirs that the US was "the only great power without a history of imperialistic claims." When Johnson sent troops to topple an elected government in the Dominican Republic in 1965, he insisted: "Over the years of our history our forces have gone forth into many lands, but always they returned when they were no longer needed. For the purpose of America is never to suppress liberty, but always to save it."

The history of denial is as long as the history of intervention and that goes back to the first decades of the republic, when US forces engaged in military action to protect US shipping in the Mediterranean, the Caribbean, Sumatra and Peru. In US foreign policy, respect for the sovereignty of others has always come second to commercial interests. By the end of the 19th century, the US had annexed Hawaii, along with dozens of smaller islands across the Pacific, and used military force to secure a foothold in the markets of China and Japan.

When it prised the Philippines, Cuba and Puerto Rico from the dying Spanish empire in 1898, the US declared "a new day of freedom" in these "liberated" lands. Filipinos took the rhetoric seriously and rebelled against the imposition of US rule. After more than a decade of brutal counter-insurgency, a quarter of a million Filipinos had been killed, and 4200 Americans. This was ten times the number of Americans killed in the brief Spanish-American War. Yet US history textbooks routinely assign far more space to the latter than the former.

America, Woodrow Wilson declared, was "the only idealistic nation in the world". He proclaimed "national self-determination" as the cornerstone of a new world order, but deployed US military forces overseas more frequently than any of his predecessors: against Mexico, Haiti, the Dominican Republic, Cuba, Panama, Nicaragua and the nascent Soviet Union.

Thanks to history textbooks, Hollywood, television and politicians (Democrat and Republican), the US people are kept in ignorance of their imperial past. Each intervention is presented as an altruistic response to a crisis. Since there is no American empire, no pattern, habit or system of extra-territorial domination, the motive for each intervention is assessed at face value. Somehow the principles of liberty and human happiness always seem magically to coincide with American national self-interest or, more precisely, the economic interests of the US elite.

In recent years, the fact that America is an empire has become less of a secret, even to Americans. Commentators such as Robert Kaplan and Niall Fergusson have urged the US to abandon its blushes and face up to its imperial responsibilities. In a new twist on "the white man's burden" (which Kipling urged on the US at the time of the Philippine War), they argue that empires have been and can be benign, and that the US is a liberal empire, or, in the words of Michael Ignatieff, "an empire lite, a global hegemony whose grace notes are free markets, human rights and democracy".

The appeal of this new imperial rhetoric seems largely restricted to sections of the intelligentsia - both liberal and conservative. Bush and US spokespersons are careful to avoid or refute it, most Americans are uncomfortable or bewildered by it, and it is simply unacceptable to those in Asia, Africa and Latin America whose lives and consciousness have been shaped by anti-colonial movements.

Opposition to foreign domination is not an emotional spasm. It is grounded in history and experience and the balance of probabilities (not least the probability that the imperial power will place its own interests before those of the people it rules). The rationalisations and even the forms of empire change but the underlying reality does not. Decisive power, military and economic, remains in the hands of a distant elite.

Whether it's talk of "empire lite" or Bush-style unilateralism, you can hear the drumbeat of the old American exceptionalism, the claim that the US has a unique destiny and that this destiny embodies the fate of humankind. History has taught peoples in many lands to fear the USA's altruism. In a poem from the early 1920s entitled 'The Evening Land', DH Lawrence wrote:

I am so terrified, America,
Of the iron click of your human contact.
And after this
The winding-sheet of your selfless ideal love.
Boundless love
Like a poison gas.