US Army Secretary Dan Driscoll has held unannounced talks with Russian officials in Abu Dhabi as part of an intense new push by President Donald Trump's administration to end the war in Ukraine and more meetings were expected on Tuesday.

The talks come as US and Ukrainian officials sought to narrow the gaps between them over a peace plan, with core issues still unresolved and Ukraine wary of being strong-armed into accepting a deal largely on the Kremlin's terms.

The exact nature of the talks in Abu Dhabi, which were confirmed to Reuters by a US official, were not immediately clear, and it was not known who was in the Russian delegation. The US official added that Driscoll, who has emerged as a point man for US diplomatic efforts, was also expected to meet Ukrainian officials while in Abu Dhabi.

Underlining the stakes for Ukraine, its capital Kyiv was hit by a barrage of missiles and hundreds of drones overnight in an attack that killed at least six people. Residents were sheltering underground wearing winter jackets, some in tents.

ZELENSKIY: WILL DISCUSS SENSITIVE ISSUES WITH TRUMP

US policy toward the war in Ukraine has zigzagged in recent months.

A hastily arranged summit between Trump and Russian President Vladimir Putin in Alaska in August spurred worries in Kyiv and European capitals that Washington might accept many Russian demands, but ultimately resulted in more US pressure on Russia.

The latest US peace proposal, a 28-point plan that emerged last week, caught many in the US government, Kyiv and Europe off-guard and prompted fresh concerns that the Trump administration might be willing to push Ukraine to sign a peace deal heavily tilted toward Moscow.

The plan would require Kyiv to cede more territory, accept curbs on its military and bar it from ever joining NATO, conditions Kyiv has long rejected as tantamount to surrender.

The sudden US push raises the pressure on Ukrainian President Volodymyr Zelenskiy, who is now at his most vulnerable since the start of the war in 2022 after a corruption scandal saw two of his ministers dismissed and as Russia makes battlefield gains.

Zelenskiy said on Monday that the latest proposed peace plan had incorporated "correct" points after talks over the weekend in Geneva but that sensitive issues were still to be discussed with Trump.

"As of now, after Geneva, there are fewer points, no longer 28, and many correct elements have been incorporated into this framework," Zelenskiy said in his nightly video address.

"Our team has already reported today on the new draft of steps and this is truly the right approach. The sensitive issues, the most delicate points, I will discuss with President Trump."

Zelenskiy said the process of producing a final document would be difficult. The Kremlin said it had nothing to say yet about reports of the Abu Dhabi meeting.

"Currently, the only substantive thing is the American project, the Trump project," Kremlin spokesman Dmitry Peskov said. "We believe that this could become a very good basis for negotiations."

MACRON WARNS AGAINST EUROPEAN CAPITULATION

A group of countries supporting Ukraine, which is known as the coalition of the willing and includes Britain and France, was set to hold a virtual meeting on Tuesday.

"It's an initiative that goes in the right direction: peace. However, there are aspects of that plan that deserve to be discussed, negotiated, improved," French President Emmanuel Macron told RTL radio about the US-proposed peace plan. "We want peace, but we don't want a peace that would be a capitulation."

He added that only the Ukrainians could decide what territorial concessions they are ready to make.

"What was put on the table gives us an idea of what would be acceptable for the Russians. Does that mean that it is what must be accepted by the Ukrainians and the Europeans? The answer is no," Macron added.

Ukraine should not have to accept limits on the size of its military, he said. Macron also said frozen Russian assets are in Europe, and Europe alone can decide what to do with them.

In a separate development, Romania sent out fighter jets to track drones which breached its territory near the border with Ukraine early on Tuesday, and one was still advancing deeper into the country, the defence ministry said.

Tensions have mounted along Europe's eastern flank in recent months after suspected Russian drones breached the airspace of several NATO states.