Rejecting the protectionist tag, he also took aim at the European Union for not pulling its weight in securing a global free trade deal.
US aerospace giant Boeing is set to win a 35 billion dollar (26 billion euro) contract to build 179 aerial refueling tanker planes for the US air force after Northrop Grumman and its European partner EADS dropped out.
Kirk, talking to AFP, saw nothing to apologise about.
"We need to be very careful when we start throwing around, loosely because of one specific issue, words like protectionism," he said.
"I'm having a hard time understanding the wisdom of those that believe that the United States can only demonstrate its fidelity to free trade by creating a world where US businesses can't compete on US contracts," he added.
Rather than that, Kirk said, his "intuitive sense" was that the EU should also ask Northrop Grumman what its motives were for throwing in the towel.
"We're in a world where if we lose we run away and scream 'the process isn't fair, it's protectionism'.
"We've got to be better than that and understand the consequences of those kinds of words in a world in which more people believe that world trade has only benefitted the rich and powerful," the US trade representative insisted.
Kirk, in Brussels to take part in a major strategy forum over the weekend, said the US defence secretary was more disappointed than anyone when the European outfit pull out of the bidding process.
"It is not in the long-term interest of the United States or the European Union that you've only got two companies capable of bidding on these major contracts," he underlined.
Earlier this month, France's Europe Minister Pierre Lellouche said the suspicions that the Pentagon skewed bidding rules for the tanker jet contract in favour of a US company would have serious consequences for EU-US relations.
"One of the problems is that we don't know exactly what the United States wants. They don't want to go forward for now, that much is clear," he said of the decade-old Doha round in World Trade Organization negotiations.
Kirk countered: "The United States, by any measure, is the most open market and economy in the world."
He added that this was evidenced by the nation's 379-billion-dollar trade deficit -- "a pretty compelling response to those who argue we are protectionist."
Trade relations between the United States and the European Union are "95 percent positive," Kirk said.
He said he was very pleased with a WTO ruling this week, which he said concluded that Europe's Airbus had benefitted from illegal government subsidies.
Kirk was set to meet up with De Gucht at the annual Brussels Forum on Friday, where he would allow the EU commissioner to "clarify his remarks".
"I believe there could be a more constructive use of the commissioner's time," the US official added.
For him, the Doha talks are "closer to a more successful outcome" than a year ago when he assumed his current role.
"The EU has not engaged in the push of that process and we are where we are singularly because of the push and the efforts of the United States," he said.
Source: AFP American Edition