WASHINGTON (Reuters) - 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 reelection of the former president.

Keith Kellogg, a retired lieutenant general who served as the chief of staff to Trump's National Security Council, told Reuters 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.

Still, European officials are hungry for any information they can glean about Trump's foreign policy in the event he beats Democratic President Joe Biden in the Nov. 5 election. In recent months, foreign diplomats have regularly met with officials from Trump's 2017-2021 administration.

Among the main concerns in European capitals is how Trump will handle the war in Ukraine and America's relationship with NATO. The former president and his allies have expressed skepticism about sending more aid to Ukraine, and Trump has repeatedly criticized NATO countries for spending too little on defense.

A disastrous debate performance last month by Biden appears to have boosted Trump's odds. The former president is leading Biden by 2.1 percentage points nationally, according to a polling average maintained by website FiveThirtyEight, while Biden had a slight lead ahead of the debate.

While Kellogg did not disclose whom he met with, he posted an image on X on Monday of what he described as an "informal discussion" with Ukrainian Parliament Speaker Ruslan Stefanchuk.

In June, Reuters reported that Kellogg and another Trump adviser had presented the former president with a plan to end the Ukraine war in part by conditioning any future aid to Kyiv on Ukraine's leaders agreeing to sit down for peace talks with Moscow.

Three other former Trump foreign policy officials told Reuters they had been approached by European delegations about meeting during the NATO summit, though those meetings did not take place, mainly for logistical reasons. Those officials requested anonymity to discuss private discussions.

Separately, North Macedonian Prime Minister Hristijan Mickoski met with Richard Grenell, a former acting director of National Intelligence under Trump, according to a picture Mickoski posted on Facebook on Monday.

(Reporting by Gram Slattery; Editing by Ross Colvin and Cynthia Osterman)

By Gram Slattery