United States officials on Sunday expressed optimism that a Ukraine-Russia ceasefire deal could be reached in "weeks," with President Donald Trump expected to soon discuss the issue with Russian counterpart Vladimir Putin.Trump's envoy Steve Witkoff, who met for several hours with Putin days ago, told CNN in a televised interview: "I think the two presidents are going to have a really good and positive discussion this week.""This is a highly, very complicated situation, and yet we're bridging the gap between two sides," he said, adding that Trump "really expects there to be some sort of deal in the coming weeks, maybe, and I believe that's the case."But officials also hinted strongly that Ukraine will likely have to make some major concessions if a deal is to be reached.The United States this week proposed a halt in fighting in the war after talks in Saudi Arabia, with Kyiv accepting the proposal.United States Secretary of State Marco Rubio told CBS on Sunday that his talks a day earlier with Russian Foreign Minister Sergei Lavrov were "promising," adding, that "hopefully we'll have something to announce at some point fairly soon."Putin, however, has given no clear answer to the United States proposal, instead listing a string of conditions and raising "serious questions" over the proposition.Mike Waltz, Trump's national security adviser, suggested Sunday that Ukraine would likely have to both cede some territory to the Russians and give up any aspirations to NATO membership in the foreseeable future.Asked about speculation that a deal might require Ukraine to yield its southeastern Donbas region, much of it now under Russian control, and its NATO hopes, Waltz replied: "This is going to be some type of territory-for-future-security guarantees [deal] the future status of Ukraine."He added: "A permanent pathway into NATO, or permanent membership into NATO for Ukraine, is incredibly unlikely."Witkoff, however, said on CNN that talk of United States recognition of Russian-held territory was "a little bit premature."Russia has long drawn a line against NATO membership for Ukraine, while Kyiv has ruled out territorial concessions.In a televised CBS interview, Witkoff described future peace talks as "very complicated," listing a string of challenging topics: an end to fighting along a 1,200-mile (2,000 kilometer) border, Ukraine's incursion into Russia's Kursk region, the fate of a Ukrainian nuclear reactor, and Black Sea port access.But he struck an optimistic note, saying that while the situation in Ukraine was "much more complicated" than that in Gaza, "No one's throwing their hands up in the air."He added: "Everybody is committed, all stakeholders, including the Europeans, to doing everything we need to do to get to a successful resolution."