The devastation at the World Trade Centre had to be seen to be believed and it underlined the need for the international community to adopt a multifaceted approach to deal with terrorism, the Minister for Foreign Affairs, Mr Cowen, said after spending an hour inspecting the site at "Ground Zero".
Mr Cowen was accompanied by senior officials of his Department. He said afterwards that everyone was very moved by what they saw.
"You have to be there to actually see the level of devastation, which is even greater than one would expect.
"It's hard to articulate what one feels when you see something the likes of which I have never seen before in my life."
Television pictures could not encapsulate the "sheer horror" that nearly 7,000 people were buried in the carnage.
"There are still some fires burning there, still smoke coming from the wreckage. One needs to be there to recognise just how mindless this thing is."
He was appalled at the idea that such an act could have been carried out "in the name of a God" because he believed it was a "perversion" of a respected world religion like Islam.
"There is a bipartisan unanimous view at political level in the US that things are changed for good from now on."
There were implications in this for the Irish peace process and a need to recognise that outstanding issues had to be resolved as a matter of urgency, he said.
"Lines have been drawn as a result of the outcome of September 11th."
He also met the Mayor of New York, Mr Rudolph Giuliani, as well as fire and police department chiefs.
"I conveyed to (the mayor) once again our sympathy and our admiration for the very strong and compassionate leadership he has shown this city."
The mayor noted that many Irish-Americans in the emergency services had died in the disaster: "The names were tripping off his tongue."
The Minister said his visit to Ground Zero had been an "eye-opening" experience.
"I just hope that people recognise that this is a continuing threat and we have to be very resolute, very determined, to deal with it." A multifaceted political, diplomatic and economic approach was needed.
He said the US was assessing its options and "what, if any" military action might be taken. The Secretary of State, Mr Colin Powell, whom he met earlier in the week, had said any military response would be careful and calibrated.
"I am very impressed by the very calm and measured way in which the Bush administration has been seeking to address this issue," Mr Cowen said.
People needed to "take on board" the nature of the attacks on the World Trade Centre and the Pentagon.
"There are no moral constraints on those who have done this. The only constraints they have are technical and logistical."
When asked if he still believed it was correct to offer the US overflight and landing facilities in the current crisis, he said: "We have a responsibility as members of the Security Council to demonstrate that, within the limited means available to us, we are prepared to do what is necessary."
He rejected suggestions that Irish neutrality was compromised, pointing out that there was no question of joining a mutual defence pact.
"Ireland is not neutral in relation to international terrorism," he said, adding that the Government had a responsibility under international law to see that UN resolutions were implemented.
He failed to see how our credibility could be maintained or enhanced if, having voted for Security Council Resolution 1368 condemning the atrocities, Ireland then sought to "resile" from making facilities available for its implementation.