Story highlights Tillerson has been slammed for allegedly hollowing out America's oldest government agency

"I'm offended on their behalf when people say somehow we don't have a State Department that functions. I can tell you its functioning very well from my perspective," Tillerson said

Washington (CNN) Secretary of State Rex Tillerson hit back at critics, including lawmakers, who charge that he is hollowing out America's oldest government agency and undermining diplomacy at a time of deepening international crises.

Speaking at the Wilson Center on Tuesday, the former ExxonMobil CEO defended his reorganization plan for the State Department, as well as proposed budget cuts of as much as 30 percent. Citing the hard work of staff who keep the agency running day to day, Tillerson said he was offended by all those who declare the State Department isn't working.

"I'm offended on their behalf when people say somehow we don't have a State Department that functions. I can tell you its functioning very well from my perspective," Tillerson said in a question and answer session after remarks about the US-Europe relationship.

"Can we really keep this up?"

Outlining his thinking behind the cuts and agency reorganization, Tillerson noted that the State Department budget was at a record high of $55 billion in 2016. "Quite frankly, it's just not sustainable," the top US diplomat said of those spending levels. By comparison, the Pentagon budget in 2016 was roughly $585 billion.

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