Several high-ranking European officials have met with a top foreign policy adviser to Donald Trump during the ongoing NATO summit in Washington this week, as America's allies gird for the possible re-election of the former president.

Keith Kellogg, a retired lieutenant general who served as the chief of staff to Trump's National Security Council, said he has met several European officials in recent days, including foreign ministers. He did not disclose the identities of those foreign officials nor what was discussed during those talks.

Kellogg, who is in regular contact with Trump, has emphasized that he does not speak for the former president nor his campaign.