By Erin Banco

MUNICH (Reuters) - A senior U.S. official on Thursday said the United States had not ruled out potential NATO membership for Ukraine or a negotiated return to its pre-2014 borders, contradicting comments made this week by the U.S. defense secretary ahead of possible peace talks to end the Ukraine war.

"Right now, that is still on the table," said John Coale, President Donald Trump's deputy Ukraine envoy, when asked whether the U.S. had ruled out possible NATO membership for Ukraine. Speaking in an interview with Reuters in Munich, he added that a possible return to Ukraine's pre-2014 lines was also still on the table.

On Wednesday, U.S. Defense Secretary Pete Hegseth delivered a different message, telling Ukraine's military allies in Brussels that a return to Ukraine's pre-2014 borders was unrealistic and that the U.S. does not see NATO membership for Kyiv as part of a solution to the nearly three-year-old Ukraine war. His comments sparked concern that the U.S. had made concessions to Russian President Vladimir Putin even before the start of talks.

Speaking after Coale's comments, Trump told reporters in the White House that he did not believe Russia would "allow" Ukraine NATO membership, blaming President Joe Biden's administration for broaching the subject in the first place.

"I believe that is the reason the war started," Trump said. "Biden shouldn't have said that."

Earlier on Thursday, Hegseth appeared to backtrack on his own remarks, telling a press conference that "everything is on the table" for Ukraine war negotiations and that it was up to Trump to decide what concessions will be made.

Trump on Wednesday ordered his top officials to begin talks on ending the war.

The opposing messages on Ukraine come as Coale is in Munich this week with General Keith Kellogg, Trump's lead Ukraine envoy, for the annual Security Conference. Kellogg's name did not appear on a Wednesday announcement from the president that listed which cabinet officials would lead the formal peace talks.

Steve Witkoff, the U.S. Middle East envoy, will now be helping on negotiations, taking the lead on talks with Russia, Coale said. Kellogg and Coale are both involved in talks with the Europeans and Ukrainians, he said.

Asked about Kellogg's role in peace talks, White House press secretary Karoline Leavitt said on Wednesday that Kellogg "remains a critical part of this team and this effort."

EUROPEAN INVOLVEMENT

Coale said that formal negotiations on Ukraine had not yet begun and that the U.S. was still working through discussions with the Europeans and Ukrainians about how best to end the conflict.

"Where do the Ukrainians and Europeans fit into all of this? At this point we don't know," Coale said, adding that you "have to have the Europeans involved."

"The Europeans want this war stopped," he said. "They are more than willing to participate (in supporting Kyiv militarily). There are doubts ... as to whether they are going to give 100 percent. But everything I am hearing indicates they are willing to really get in there."

It is unclear what exactly Washington has communicated to the Kremlin about negotiations. But Coale said Putin appears to be willing to enter negotiations with Ukraine, without preconditions.

"There's been a lot of talk about the trip Steve Witkoff took to Moscow and how he met with Putin," Coale said. "Putin seems to be willing to play ball, but we're not sure what that means. I think he's ready to talk."

Ukrainian President Volodymyr Zelenskiy warned Western officials on social media on Thursday not to trust Putin, who launched his full-scale invasion of Ukraine in February 2022.

Officials in Europe have expressed deep concerns about Hegseth's Wednesday comments.

"We shouldn't take anything off the table before the negotiations have even started. Because it plays to Russia's court," Kaja Kallas, the European Union's high representative for foreign affairs and security policy, told reporters on Thursday.

"It is appeasement. It has never worked."

Asked if the U.S. was conceding too much to Putin upfront, Coale said: "Some people talked out of turn, but I don't think we're conceding anything."

"You don't know with Putin and the Russians," Coale said. "Are they trying to play us? Or are they sincere? And then you get to a table and you find out fast."

(Reporting by Erin Banco; Editing by Don Durfee and Rosalba O'Brien)