Sen. Susan Collins, R-Maine, is the first GOP senator to say publicly she will vote for the bipartisan compromise on expanded background checks for the sale of guns online and at gun shows. NBC's Kelly O'Donnell reports.

Speaking exclusively to NBC News, Sen. Susan Collins, R-Maine, is the first GOP senator to say publicly she will vote for the bipartisan compromise on expanded background checks for the sale of guns online and at gun shows.

Collins said "I do intend to support it" now that she has reviewed the actual text of the Manchin-Toomey bill and calls it a "reasonable" approach. Collins described the Manchin-Toomey effort as "a responsible break through from two people who have far better NRA rankings than I have." Both Sens. Joe Manchin, a Democrat from West Virginia and Pat Toomey, Republican of Pennsylvania, hold "A" ratings from the National Rifle Association. Collins added she knows her yes vote and support is "not a popular thing in my state."

Sen. Mark Kirk, R-Ill., worked with Manchin and Toomey privately during negotiations and is expected to vote yes on the background checks bill.

Collins, who is running for re-election next year, said she would not have supported a plan that required universal background checks, including individual sales. She cited an example of a father who gives his daughter a gun for protection when she "moves to the big city."

Collins pointed out that her state has among the highest rate of gun ownership in the country at more than 40 percent while also ranking as the safest state with respect to low violent crime.

The three-term Republican says she is "being hit hard" and "being besieged by all sides" referring to ads run against her by both the conservative National Association of Gun Rights and the president's group, Organizing for America.

After a week when Newtown families paid visits to senators urging new, tighter measures on gun sales, Collins said, "I am furious and beside myself" over a depiction of her in a press account concerning Newtown families on Capitol Hill.

Collins told NBC News, "I was willing to make the choice to be late for the president in order to meet with the grieving families," adding, "I truly felt it was more important."

Known for being punctual, Collins described her unusual dilemma.

"I realized I was in a real bind" and told staffers "to call the White House." Collins had never been invited to attend a small dinner with the president before. "How rude is that? Tell the president you're going to be late to dinner," she told NBC News.

Collins explained the families were expected at her office at 5 p.m. Wednesday but arrived late, at the time she was scheduled to depart for the White House about 5:45 p.m.

"I said, I have to meet with them, my heart goes out to them." Collins said three of the family members gave her photos of their loved ones and "those are on my desk to this moment."

"I was so moved by them," she added.

Collins remembered telling the families about her own reaction after seeing their appearance on "60 Minutes" earlier in the week.

"I wept, I literally wept."

The senator and families also discussed the substance of gun measures being considered by Congress for about 20 minutes. Collins had not told the families her vote would a "yes" on the Manchin- Tommey compromise because she had not received the actual text at that time. She told them she knew it would come up at her meeting with the president. "I listened to them and I treated them with the compassion they deserved."

Collins said when she arrived 45 minutes late to the White House dinner she was "embarrassed." She added: "The salad plates were being cleared."

Collins said she went up to President Barack Obama and explained why she was late. She said the president was gracious, saying: "Good call. I totally understand. It's fine."

Collins recalled saying, "Mr. President, I am never late and I feel really bad, but it would be cruel to not meet with them even for the President of the United States. And cruel is the word I used."

Collins is clearly frustrated by a report that she says left the wrong impression that her office had offered families a meeting with staffers and only a quick visit by the senator herself and that was rejected by the families' handlers.

Collins said firmly, "I'm not someone who would blow off grieving families." She also insisted she is not blaming the families for making her late for dinner with President Obama.

She also said that unlike other senators who allowed media and cameras into their meetings, she "did not want to put the families on display." But Collins said she almost regretted that decision now because it would have confirmed her effort to spend time when them.

"I can take being attacked by right-wing nutty groups, but to be attacked that I somehow was unkind or cruel to Newtown families I cannot take. It's not true."

Collins is a critical "yes" vote for the families and Democrats who need Republican support to pass expanded background checks.

Collins knows her support is valuable to the Newtown families.

"I am an important vote for them but I truly care about them."

Related: