North Carolina House Speaker Thom Tillis's (R) campaign won't take a position on Sen. Richard BurrRichard BurrWhen education is an ignored national security matter Five takeaways from a busy day of Russia hearings Rubio: 'All options should be on table' if Flynn refuses new subpoenas MORE's (R-N.C.) controversial letter criticizing veterans groups though he's bashed Sen. Kay HaganKay HaganLinking repatriation to job creation Former Sen. Kay Hagan in ICU after being rushed to hospital GOP senator floats retiring over gridlock MORE (D-N.C.) for what he calls a slow response to the Department of Veterans Affairs scandal.

Burr wrote a letter saying the Washington leaders of most national veterans groups had "ignored the constant VA problems expressed by their members and is more interested in their own livelihoods and Washington connections than they are to the needs of their own members."

Veterans groups, including the Veterans of Foreign Wars, Disabled American Veterans and Paralyzed Veterans of America issued furious responses to the controversial open letter, which was released to the public just before Memorial Day weekend.

Tillis had criticized Hagan for not immediately calling for Veterans Affairs Secretary Eric Shinseki's resignation (she did this week, before he stepped down on Friday). But his campaign didn't want to comment on Burr's letter.

"As far as the op-ed and the effort Sen. Burr is making, we're not going to get into the logistics of the letter, but the bottom line is that we need to make sure our veterans are getting the services they deserve, and it's become pretty apparent to everyone that's not the case," Tillis campaign manager Jordan Shaw told The Hill on Wednesday before promising to follow up with a more detailed response.

"We don't have access to the same information that Sen. Burr does, but what we have seen over the last several weeks is a clear indication that Sen. [sic] Shinseki should resign in an effort to ensure that our Veterans receive the services they deserve," Shaw said in a follow-up statement on Friday, shortly after Shinseki had resigned. "While Sen. Burr has spoken out about the issue, Sen. Hagan remained silent until it became politically damaging for her to continue her silence.  We must do everything we can to ensure that those who have served our country are being served appropriately by the agencies they rely on."

North Carolina has a high number of military bases and veterans.