On Tuesday, Jay Carney, the White House press secretary, said the launch of a rocket would hinder the promised aid.
"It's impossible to imagine that we would be able to follow through [and] provide the nutritional assistance that we had planned on providing, given what would be a flagrant violation of North Korea's basic international obligations," Carney said.
Gregg said that given North Korea's history of honoring important events in its regime with extravagant displays of propaganda, the U.S. should have anticipated the country would do something to honor founder Kim Il Sung's birthday.
"It's unfortunate the timing is how it is," he said, adding that he hoped the U.S. would send an envoy to North Korea to work on building a dialogue.
"The obstacle to that is domestically here. The Republicans would be all over anything like that as appeasement," he said. " For Obama to do this in an election year is unlikely."
The rocket launch is the first under Kim Jong Un. The regime's leader, who is believed to be 29 years old, assumed party leadership in January of this year, weeks after the death of his father.