Russia and Ukraine achieved their most significant progress yet in peace negotiations on Tuesday, with Moscow promising to reduce “by multiples” the intensity of its military activity around Kyiv and to its north.

Ukrainian officials for the first time outlined potential concessions over territory occupied by Russia, proposing that negotiations about the status of Crimea — the Ukrainian peninsula that Moscow seized and annexed in 2014 — be conducted over a period of 15 years, with Ukraine refraining from trying to retake the peninsula by force.

The issue of the eastern Ukrainian region known as the Donbas, which Russia no longer recognises as part of Ukraine, could be discussed in negotiations between President Vladimir Putin of Russia and President Volodymyr Zelensky of Ukraine, an aide to Zelensky said after Tuesday’s talks.

Zelensky has for months sought a meeting with Putin to resolve their differences, efforts the Kremlin has deflected, saying that it was too early to talk. On Tuesday, Russia said it was now ready to accelerate preparations for such a meeting, and that it could be held as soon as a draft peace agreement with Ukraine was ready.

“If the treaty is worked out quickly and the required compromise is found, the possibility of making peace will be much closer,” Vladimir Medinsky, the head of the Russian delegation, told reporters after the talks, which were conducted in Istanbul and hosted by President Recep Tayyip Erdogan of Turkey.

While Ukraine and Russia still appeared to be a long way from making peace, both sides sounded more conciliatory on Tuesday than at any other point since Putin’s invasion began on February 24. Medinsky said that Russia viewed Ukraine’s proposals “a constructive step in the search for a compromise”.

The key to a peace agreement appeared to be Ukraine’s willingness to adopt a neutral status — including not joining the Nato alliance or hosting western troops — in exchange for international “security guarantees”. The head of the Ukrainian delegation, David Arakhamia, said Ukraine was already discussing such guarantees with other countries in order to create a “working security mechanism” that would assure Ukraine’s sovereignty.

“We have discussed all contentious issues, more or less,” Mykhailo Podolyak, an aide to Zelensky, said in Istanbul. He told Turkish reporters later that Ukraine was ready to “take a pause of 15 years” on the issue of Crimea. Putin had warned in the run-up to the invasion of Ukraine that if Ukraine were to join the western military alliance and seek to retake Crimea, there could be a war between Russia and Nato.

“The Russian delegation is constructive,” Podolyak said. “This doesn’t mean that the negotiations are easy. They are difficult.”

A deputy Russian defence minister who joined the talks in Istanbul, Aleksandr Fomin, said that Russia was prepared to reduce its military activity in parts of Ukraine because the two sides had moved the talks “into the practical plane” on key issues like the neutrality and non-nuclear status of Ukraine, as well as the security guarantees Ukraine is seeking.