Kyiv has now expressed readiness to drop its bid to join the NATO military alliance if the U.S. and other Western nations give it similar security guarantees.

German Chancellor Friedrich Merz, right, welcomes U.S. negotiator Jared Kushner, second right, and US special envoy Steve Witkoff, second left, at the Chancellery for talks with Ukrainian President Volodymyr Zelenskyy on Sunday, in Berlin. Bergmann/Bundesregierung via Getty Images

Ukraine`s top peace negotiator said Monday that U.S. and Ukrainian officials had achieved "real progress" in the second round of peace talks in Berlin aimed at ending Russia`s war.

"Over the past two days, Ukrainian-U.S. negotiations have been constructive and productive, with real progress achieved," Rustem Umerov, secretary of the National Security and Defense Council, wrote on X.

"The American team led by Steve Witkoff and Jared Kushner are working extremely constructively to help Ukraine find a way to a peace agreement that lasts."

Ukraine faces Washington`s pressure to swiftly accept a U.S.-brokered peace deal in the face of an increasingly assertive Moscow.

There were no immediate comments from the U.S. on the talks in Berlin that involved President Donald Trump`s special envoy Steve Witkoff and Trump`s son-in-law Jared Kushner, as well as European officials, which lasted roughly 90 minutes after a five-hour session Sunday.

The U.S. government said in a social media post on Witkoff`s account after Sunday`s meeting that "a lot of progress was made."

The search for possible compromises has run into major obstacles, including control of Ukraine`s eastern Donetsk region, which is mostly occupied by Russian forces.

Zelenskyy has now expressed readiness to drop Ukraine`s bid to join the NATO military alliance if the U.S. and other Western nations give Kyiv security guarantees similar to those offered to NATO members.

But Ukraine continued to reject the U.S. push for ceding territory to Russia. Russian President Vladimir Putin wants Ukraine to withdraw its forces from the part of Donetsk region still under its control among the key conditions for peace.

Zelenskyy`s itinerary on Monday also included meetings with German and other European leaders.

"The issue of security in particular will ultimately determine whether this war actually comes to a standstill and whether it flares up again," a spokesperson for German Chancellor Friedrich Merz, Stefan Kornelius, told reporters.

The Russian president has cast Ukraine`s bid to join NATO as a major threat to Moscow`s security and a reason for launching the full-scale invasion in February 2022. The Kremlin has demanded that Ukraine renounce the bid for alliance membership as part of any prospective peace settlement.

Zelenskyy emphasized that any Western security assurances would need to be legally binding and supported by the U.S. Congress.

The Kremlin said Monday it expected to be updated on the Berlin talks by the U.S. side.

Asked whether the negotiations could be over by Christmas, Kremlin spokesperson Dmitry Peskov said trying to predict a potential time frame for a peace deal was a "thankless task."

"I can only speak for the Russian side, for President Putin," Peskov said. "He is open to peace, to a serious peace and serious decisions. He is absolutely not open to any tricks aimed at stalling for time."

Putin has denied plans to attack any European allies.

In London, meanwhile, the new head of the MI6 spy agency was set to warn on Monday how Putin`s determination to export chaos around the world is rewriting the rules of conflict and creating new security challenges.

Blaise Metreweli was using her first public speech as chief of the United Kingdom`s foreign intelligence service to say that Britain faces increasingly unpredictable and interconnected threats, with emphasis on "aggressive, expansionist" Russia.

Russia fired 153 drones of various types at Ukraine overnight Sunday into Monday, according to Ukraine`s Air Force, which said 133 drones were neutralized, while 17 more hit their targets.

In Russia, the defense ministry on Monday said forces destroyed 130 Ukrainian drones overnight. An additional 16 drones were destroyed between 7 a.m. and 8 a.m. local time.

Eighteen drones were shot down over Moscow itself, the defense ministry said. Flights were temporarily halted at the city`s Domodedovo and Zhukovsky airports as part of safety measures, officials said.

Damage details and casualty figures were not immediately available.