President Donald Trump on Tuesday pledged that American troops would not be on the ground in Ukraine — but provided little other insight into the scale of U.S. security guarantees as he pushes to end Russia’s war on its neighbor.

“You have my assurance, and I’m president,” Trump said on “Fox & Friends,” when asked what assurances he has that there won’t be American boots in the country to defend against another Russian incursion.

There is room for U.S. military involvement that doesn’t require American troops in Ukraine, including air or drone support or non-combat roles. In fact, a senior administration official, granted anonymity to discuss private conversations, told POLITICO on Monday that there isn’t a red line on a U.S. role, adding that the U.S. could participate in a peacekeeping force if it is the last piece required for a deal.

The comments — Trump’s first since Monday’s White House meeting with Ukrainian President Volodymyr Zelenskyy and European leaders — come after an intense few days of negotiations. During a summit in Alaska, Russian President Vladimir Putin expressed openness to security guarantees.

But the details of those security guarantees could remain a sticking point internationally.

“We haven’t even started [that discussion] other than a commitment,” another senior administration official, also granted anonymity, told POLITICO. “The question is, ‘Who participates to what percentage?’”

Trump on Tuesday stressed that Ukraine would not join NATO, but that Ukraine would have security protections Europe would “front load.” He said “a couple” countries — including France, Germany and the United Kingdom —want to have “boots on the ground.”