MOSCOW—Russia called on the U.S. to push Kiev into giving up its military campaign against pro-Russia rebels in eastern Ukraine and negotiating a political deal, as recent Ukrainian gains on the battlefield were reversed by what Western officials called an influx of Russian men and materiel.

Foreign Minister Sergei Lavrov said Washington should pressure Ukrainian President Petro Poroshenko to reach a deal during his planned visit to the U.S. later this month.

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