German Chancellor Angela Merkel offered reassurances on Sunday that Ukraine would not suffer as a result of the Germany-Russia Nord Stream 2 pipeline, but Ukraine said talks about its future as a transit country had been vague.

During Merkel's visit to the capital Kiev on Sunday, Ukrainian President Volodymyr Zelensky warned that the soon-to-be completed Nord Stream 2 carrying Russian gas to Europe was "a dangerous geopolitical weapon".

The two leaders' meeting in Kiev took place before Merkel leaves office next month after 16 years in power.

Merkel said gas should not be used as a geopolitical weapon and that Germany could impose new sanctions on Moscow if necessary.

"It is important that Ukraine remains a transit land," she said after talks with Zelensky. She called for Ukraine's existing transit deal with Russia to be extended beyond its 2024 expiry, adding that Germany would support Ukraine's gradual transition to renewable energy.

Germany has given financial assistance and diplomatic backing to Ukraine since 2014. But Kiev has bitterly opposed a deal between Berlin and Washington over Nord Stream 2.

Bypassing Ukraine and depriving the Western ally of essential gas transit fees that Kiev estimates to be at least $1.5 billion per year, Nord Stream 2 is set to double Russian natural gas shipments to Germany, Europe's largest economy.

"We view this project exclusively through the prism of security and consider it a dangerous geopolitical weapon of the Kremlin," said Zelensky during a joint news conference with Merkel.

Though the main risks after completion of the pipeline beneath the Baltic Sea would be "borne by Ukraine", he said it would also be dangerous "for all of Europe".

Contract past 2024

Merkel's visit came two days after she met Russian President Vladimir Putin on her last official visit to Russia, where she had also pressed Putin on Ukraine's status as a transit country.

Putin told reporters that Moscow was ready to extend the transit agreement beyond 2024, but that it needed more details.

A deal reached by the United States and Germany in July included a commitment to helping Ukraine continue to receive transit fees once Nord Stream 2 becomes operational.

But Yuriy Vitrenko, head of Ukraine's state energy firm Naftogaz, said last month he did not think Russia would continue to transit any gas through Ukraine beyond 2024.

Merkel also wants more progress in peace talks over eastern Ukraine, and on Sunday called for "Normandy format" negotiations among the leaders of Germany, France, Russia and Ukraine.

"This would enable progress, in my opinion," she said. "I'm pleased that Zelensky said he would be prepared to do so."

Merkel sought to reassure Zelensky, stressing her commitments to support Ukrainian government forces are binding on future German governments.

However, the Ukrainian leader said that while he and Merkel had discussed the extension, he had heard only "very general things".

Despite Germany's refusal to sell weapons to Ukraine, Zelensky said Kiev was still "counting on it and expecting it".