Ukrainian Presidential Adviser Mykhailo Podolyak said that Ukraine insists on a system of security guarantees as one of the key elements of negotiations with Russia, the presidential press service reported on Saturday.

During an interview with German media, Podolyak stressed that such a system "is impossible without the participation of the United States in the first place."

According to the negotiator, the future of Crimea and certain areas of Donetsk and Luhansk should be decided only by the presidents of Ukraine and Russia.

He called on Ukraine's partners to provide air defense systems and give weapons to "adequately help" Kyiv, adding that sanctions, such as oil embargoes and restrictions on financial transactions, are also needed.

Ukrainian and Russian delegations have held three rounds of in-person peace talks in Belarus since February 28. The fourth one started on March 14 in a video conference format.

Commenting on the progress of the ongoing negotiations, Russian Foreign Ministry's spokeswoman Maria Zakharova Sunday said the situation currently is neither good nor bad adding that sometimes it's tense and at other times loose.

Earlier this week, the head of the Russian delegation Vladimir Medinsky said there has been a convergence of views on minor issues during the ongoing talks, but not much progress has been made on major political matters.

He also said an agreement between Moscow and Kyiv can only be reached if all of Russia's major concerns are addressed.

(With input from Xinhua)