To boost confidence in a cease-fire in eastern Ukraine, both sides in the conflict should pull back weapons under 100 mm caliber from the front line, Russia’s foreign minister said Saturday.

Sergei Lavrov said a common aim of the cease-fire, negotiated in Minsk in February, was to have it hold indefinitely, though some violations have occurred.

Lavrov said parties involved in the conflict, as well as the Organization for Security and Cooperation in Europe, were discussing ways to supplement the Minsk agreement. Among other measures, the agreement calls for pulling back weapons with caliber over 100 mm, including large artillery, heavy mortar and powerful rocket systems.

“There is a possibility to pull back troops with caliber under 100 mm,” Lavrov said at a news conference during a visit to Slovakia. “… We will try to help the sides to reach such an agreement, which would increase mutual confidence.”

His remarks echoed comments by a Kyiv official last week that weapons not covered by the Minsk agreements, such as tanks and 80 mm mortar and other weapons of up to 100 mm caliber, may be pulled back.

Lavrov criticized a Ukrainian law on the status of eastern Ukraine, which he said ran counter to the Minsk cease-fire agreement.

Ukraine’s parliament voted in March to offer limited self-rule to pro-Russian rebels in the east. But Kyiv insisted the law should come into force only when elections are held in the eastern territories under Ukrainian jurisdiction, drawing immediate criticism from Russia.

Asked about the rights of Crimea Tatars after Russia annexed the peninsula last year, Lavrov said they had full rights to use their language and were represented in power structures.