Pentagon officials are close to finalizing a plan to send a Patriot air defense missile system to Ukraine amid the ongoing conflict between Kyiv and Moscow, US officials said on Tuesday.

The United States is "poised" to provide at least one Patriot missile battery to Ukraine once the plan is approved, one of the officials said. The approval is likely to come later this week, said three officials, who spoke on condition of anonymity because the decision is not final and has not been made public.

The Pentagon's plan still needs to be approved by Defense Secretary Lloyd Austin before it is sent to US President Joe Biden for his signature.

The Patriot system is highly mobile, and uses ground-based radar to locate and track aerial threats that can then be shot down with a surface-to-air missile. Initially designed to take out aircraft, upgrades over the years have made the system effective at intercepting ballistic and cruise missiles.

Ukraine has been calling for the US to send the advanced long-range air defense system that is highly effective at intercepting ballistic and cruise missiles.

The Pentagon declined to comment on reports about the Patriot system at a news briefing.

Dmitry Medvedev, deputy chairman of the Russian Security Council, has warned NATO against providing Ukraine with Patriot missile defenses, and it is likely Moscow will view the move as an escalation.

In Kyiv, Ukrainian authorities reported explosions in the capital on Wednesday, saying two administrative buildings were hit in a downtown district that is home to many government buildings. It was not immediately clear whether there were any casualties.

In Paris, Ukraine's Western allies pledged an additional 1 billion euros ($1.1 billion) in emergency winter aid on Tuesday, responding to pleas from Ukrainian President Volodymyr Zelensky.

Around 70 countries and international organizations gathered in Paris for a meeting aimed at enabling Ukrainians "to get through this winter", French President Emmanuel Macron said.

In Brussels, the European Union energy ministers' meeting on Tuesday failed to strike a final deal on a blocwide cap on natural gas prices, after months of debate among member countries over whether the measure can ease Europe's energy crisis.

Agencies contributed to this story.