Moscow, Russia - Russian President Vladimir Putin has threatened to retaliate with cluster bombs if Ukraine uses these US-supplied munitions against his forces.

"I want to say that Russia has sufficient reserves of various types of cluster munitions," Putin said in a clip released on Russian state TV.

Russia does not want to use the internationally outlawed munitions, he insisted, "but of course, if it is used against us, then we reserve the right to take congruent actions."

Earlier, Russian Defense Minister Sergei Shoigu made similar comments.

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Human rights activists have accused both Russian and Ukrainian forces of already using cluster bombs. Putin denied this, even though he admitted that for a time there was a "shortage of the ammunition" on the Russian side.

The Russian leader claimed the US is providing the controversial cluster munitions because the West was no longer able to supply Ukraine with sufficient conventional weapons.

"They have found nothing better than to propose the use of cluster munitions," Putin said.

With the newly-arrived cluster munitions, Ukraine hopes to accelerate its major offensive to retake its own territories in the east and south.

The bombs, which explode above the ground, spread projectiles over larger areas. Because many of them often do not explode immediately, they, like mines, are considered a danger to civilians even after hostilities have ended.

Ukraine said Sunday its forces were on the defensive against Russian assaults near the eastern city of Kupiansk, while noting gradual progress near the hotspot city of Bakhmut.