WASHINGTON, Dec 21 (AFP) - The United States said on Wednesday (Dec 21) it would provide Ukraine with the advanced Patriot air defence system to help counter Moscow's relentless aerial attacks.

The system is part of US$1.85 billion in assistance unveiled in parallel with a visit to Washington by Ukrainian President Volodymyr Zelenskyy, his first trip outside the country since Russia invaded in February.

The announcement is a significant victory for Kyiv, which had repeatedly pushed Washington for the Patriot system, and a strong sign of US support for Ukraine.

"Today's assistance for the first time includes the Patriot Air Defence System, capable of bringing down cruise missiles, short-range ballistic missiles, and aircraft at a significantly higher ceiling than previously provided air defence systems," US Secretary of State Antony Blinken said in a statement.

The security assistance package features one Patriot battery, which consists of a command centre, a radar station to detect incoming threats, and missile launchers.

It also includes tens of thousands of rounds of artillery, rocket and tank ammunition, mortar systems, grenade launchers and body armor.

Ukraine's air defences have played a key role in protecting the country from strikes and preventing Moscow's forces from gaining control of the skies.

But as Russia faced increasing setbacks on the ground, it began systematically targeting critical infrastructure in Ukraine in attacks that have disrupted electricity, water and heat to millions of people.

Made by Raytheon, the MIM-104 Patriot is a surface-to-air missile (SAM) system initially developed to intercept high-flying aircraft.