Visiting U.S. Secretary of Defense James Mattis said Thursday that the United States is reviewing the possibility of sending lethal weapons to Ukraine.

"We are committed to continue providing you with assistance in your efforts to protect your country, the people of Ukraine," Mattis told reporters after meeting with Ukrainian President Petro Poroshenko.

He said Washington also supports Kiev's efforts aimed at reforming Ukraine's defense and security sector in accordance with international standards.

Russian Deputy Foreign Minister Sergey Ryabkov said earlier in August that deliveries of lethal arms would destabilize the situation in Ukraine, in particular in its southeast.

Kremlin spokesman Dmitry Peskov has said that such deliveries would not contribute to the peaceful resolution of the conflict between Kiev and two self-proclaimed republics in the southeast of Ukraine.

Mattis arrived in Kiev earlier in the day for a one-day visit to take part in Ukraine's Independence Day celebrations. He became the first U.S. secretary of defense to visit Ukraine in 10 years.