The memo also says the US is only having “mixed” results in its fight against al-Qaeda and questions whether the US really knows whether it is winning the war on terrorism.
It was sent to the Pentagon’s senior civilian and military leaders last week and was first reported in the USA Today newspaper.
But officials have moved to play down its significance, despite the fact it is completely at odds with Mr Rumsfeld’s more upbeat public comments.
White House and Pentagon officials said the defence secretary was merely sounding out senior colleagues on long-term issues.
Mr Rumsfeld wrote it was not possible to transform the Defence Department quickly enough to effectively fight the anti-terrorism war.
He asked: “Is our current situation such that ‘the harder we work, the behinder we get’?”
“It is pretty clear that the coalition can win in Afghanistan and
Iraq in one way or another, but it will be a long, hard slog,” he said.
Posing challenging questions to the military Joint Chiefs of Staff and others, he said the US had no way of measuring progress in the anti-terrorism war launched after September 2001.
He wrote: “Today, we lack metrics to know if we are winning or losing the global war on terror.
“Are we capturing, killing or deterring and dissuading more terrorists every day than the madrassas and the radical clerics are recruiting, training and deploying against us?”
He said little effort has gone into developing a long range plan to stop the next generation of terrorists even though great efforts are being made to stop terrorists.
“The cost-benefit ratio is against us! Our cost is billions against the terrorists’ costs of millions,” he wrote.
The memo comes as Mr Rumsfeld and other senior administration officials make a concerted effort to highlight progress US forces and occupation authorities have made in Iraq to offset what they see as negative press coverage.