MOSCOW, Dec 14 (AFP) - The Kremlin said on Wednesday that U.S. Patriot missile defence systems would be a legitimate target for Russian strikes against Ukraine, should the United States authorise them to be delivered to support Kyiv.

Washington is finalising plans to send the Patriot missile defence system to Ukraine, a decision that could be announced as soon as this week, three U.S. officials told Reuters on Tuesday.

Kremlin spokesman Dmitry Peskov said Patriots would "definitely" be a target for Russia, but that he would not comment on unconfirmed media reports.

The Patriot is considered to be one of the most advanced U.S. air defence systems, including against aircraft, cruise missiles and ballistic missiles. It typically includes launchers along with radar and other support vehicles.

Russia's embassy in Washington said the proposed transfer was provocative and could lead to unpredictable consequences.

"Even without providing Patriots, the United States is getting deeper and deeper into the conflict in the post-Soviet republic," the mission wrote on its Telegram channel.

"It is the United States that is responsible for the prolongation and escalation of the Ukrainian conflict."

The Pentagon says Russia's recent surge in missile strikes in Ukraine is partly designed to exhaust Kyiv's supplies of air defences so it can dominate the skies above the country. For that reason, the United States and its allies have been delivering more air defences for Kyiv.

For the United States, this has included NASAMS air defence systems that the Pentagon says have flawlessly intercepted Russian missiles in Ukraine. Washington has so far provided Ukraine with $19.3 billion in military assistance since the start of the conflict.