KYIV, May 28 (Reuters) - Russian Foreign Minister Sergey Lavrov has reportedly cautioned Western powers against supplying Ukraine with weapons capable of hitting Russian territory, warning such a move would be a “serious step towards unacceptable escalation”.

Lavrov’s remarks, reported on Thursday by Russia’s TASS news agency, came against the backdrop of the United States and Kyiv’s other Western allies having provided Ukraine with increasingly sophisticated arms as Moscow presses ahead with its offensive in the country’s eastern Donbas region.

He was quoted by RT’s Arabic channel as saying he hoped “sane people” in Western countries would comprehend the danger of moves to further enhance Ukraine’s arsenal.

“There are still a few left there,” Lavrov said.

On Thursday, the Reuters news agency reported that Washington had held discussions with Kyiv about the danger of an escalation in the now more than three-month-long conflict if it were to launch attacks deep inside Russia, citing unnamed US and diplomatic officials.

However, the behind-the-scenes talks have not led to the imposition of explicit geographic restrictions on the use of weapons supplied to Ukrainian forces, the officials told Reuters.

The reports come as Ukraine’s Foreign Minister Dmytro Kuleba pleaded with Western nations to provide Kyiv with heavy weapons. He said in a video posted on Twitter his country needed stronger artillery as it was the “only” area in which they were outmatched by Moscow.

“If you really care for Ukraine, [send] weapons, weapons and weapons again,” Kuleba said.