"I'm surprised that it came to this and I wish it was another way, but I can't be anything other than honest with Iowans and the American people," said King on MSNBC's "Place for Politics" Tuesday.
The conservative lawmaker announced Monday he would not endorse any of the candidates prior to the Iowa caucuses.
King said despite the fact that he had planned to back one of the candidates,
he didn't feel strongly enough about any of the GOP contenders to lend his
"It was not the right thing for me to do to pick a candidate's name out of a hat or throw myself into something unless it was a genuine conviction," King said on MSNBC's "Morning Joe" earlier Tuesday.
His lack of support is big blow to candidates competing for evangelical voters, who make up the majority of Iowa caucus voters. Rick Santorum, in particular, has surged in recent days, and King's nod could have given him an even greater boost.
King, who was courted by Santorum in recent weeks, said his relationships with the other GOP hopefuls held him back in part from endorsing the former Pennsylvania senator.
"I spent a fair amount of time with Rick. I like him. I just wasn't ready to do it," King said.
King spoke highly of Santorum, but said he was not as strong on economic issues or immigration as some of the other Republican contenders.
"I didn't get up to say anything negative about Rick Santorum this morning. It's pretty hard to do that. … Economically, he's not as comfortable talking about economics as several of the other candidates and he's not as comfortable talking about immigration as several of the other candidates," said King.
However, King was quick to add that he would be comfortable with Santorum as president and praised the candidate's promise to use the presidential bully pulpit to promote family values and social conservatism.
King told MSNBC that in regards to Ron Paul's candidacy there is a lot he supports, but that he strongly opposes the Texas congressman's foreign policy position.
Paul has repeatedly called for a withdrawal of troops from overseas bases and favors a smaller U.S. presence abroad.
"Just think about bringing, collapsing the power we've projected around this globe that's been paid for in blood and treasure. Collapse it into the 50 states. What happens? Our enemies will fill the vacuum right up to our borders and that is a very scary thought," he said.
Despite criticisms by opponents of Paul's foreign policy he has remained near the top of most polls of likely Iowa caucus-goers heading into Jan. 3.
An Iowa poll released Monday showed Romney and Paul in a virtual tie, one day before the state's caucuses.
King said that although Romney didn't distinguish himself enough for an endorsement, he praised the front-runner's executive and financial experience.
"The trains would run on time, he would put professionals in every spot. It would flow down through and the executive branch would be back functioning like a real government again. That is a really good thing about Mitt," King said.
—Emily Goodin contributed.