US National Security Advisor Mike Waltz said on Thursday that President Donald Trump is “very, very frustrated” with Ukrainian President Volodymyr Zelensky, highlighting the growing tensions between the Trump administration and Kyiv.

During a White House briefing, Waltz declined to answer whether Trump holds Russian President Vladimir Putin or Zelensky more responsible for the ongoing war in Ukraine, CNN reported.

“(Trump’s) goal here is to bring this war to an end, period, and there has been ongoing fighting on both sides — it is World War I-style, trench warfare,” Waltz stated.

He added that Trump’s frustration with Zelensky stems from a lack of appreciation for US support. “There needs to be a deep appreciation for what the American people, what the American taxpayer, what President Trump did in his first term, and what we’ve done since. Some of the rhetoric coming out of Kyiv, frankly, and insults to President Trump, were unacceptable.”

Trump escalated tensions on Wednesday by calling Zelensky a “dictator without elections” on Truth Social. In response, Zelensky accused Trump of living “in a disinformation space” and “helping Putin out of his isolation.”

When asked whether Trump believes Putin is a dictator, Waltz avoided a direct response.

“President Trump is obviously very frustrated with President Zelensky — the fact that he hasn’t come to the table, that he hasn’t been willing to take this opportunity that we have offered,” Waltz said. “I think he eventually will get to that point, and I hope so very quickly.”

Waltz stressed that Trump’s priority is to stop the fighting, not dwell on past events.

“If there’s anybody in this world that can go toe to toe with Putin, with Xi, with Kim Jong Un — and you could keep going down the list — it’s Donald J. Trump. He is the deal maker in chief. There is no question that he is the Commander-in-Chief,” he added.

Meanwhile, Zelensky met with US Special Envoy Keith Kellogg in Kyiv, calling the discussion “productive” and expressing gratitude for American assistance.

“It’s important for us — and for the entire free world — that American strength is felt,” Zelensky stated on X.

His office noted that their discussions covered the battlefield situation, efforts to bring Ukrainian prisoners of war home, and security guarantees. However, a planned joint news conference was canceled at the US’ request.

The diplomatic friction follows US-led peace talks with Russia in Saudi Arabia earlier this week, which excluded Kyiv.

The war has significantly shifted since Russia’s initial invasion attempt in 2022. After being pushed back from Kyiv, Russian forces solidified control over eastern Ukraine, where they have supported separatist groups since 2014 — the same year Russia illegally annexed Crimea.

Waltz defended Trump’s approach to the war, pushing back on Ukraine’s criticism.

“Some of the rhetoric coming out of Kyiv, frankly, and insults to President Trump were unacceptable,” he said.

He also reinforced Trump’s stance that Europe must bear more responsibility for Ukraine’s defense.

“It is unacceptable that the United States, and the United States taxpayer, continues to bear the burden — not only of the cost of the war in Ukraine but of the defense of Europe,” Waltz said.

“We fully support our NATO allies. We fully support the Article Five commitment, but it’s time for our European allies to step up,” he added, urging NATO countries to increase their defense spending to 5% of GDP.