The United States on Tuesday announced a new $1.2 billion security assistance package for Ukraine to boost the country's air defenses and provide it with additional artillery ammunition.

Ukraine is readying for a highly anticipated spring offensive against invading Russian troops, but the latest assistance will not immediately arrive on the battlefield as it must still be procured from the defense industry or partners.

This avoids depleting US stocks, but means the assistance will take longer to reach Kyiv than equipment drawn directly from existing American military inventories.

The package underscores the continued US commitment to Ukraine "by committing critical near-term capabilities, such as air defense systems and munitions, while also building the capacity of Ukraine's armed forces to defend its territory and deter Russian aggression over the long term," the Defense Department said in a statement.

Ukrainian President Volodymyr Zelensky hailed the new assistance, saying on Twitter that "we appreciate this sign of solidarity with Ukraine shown on a symbolic day for us -- Europe Day and the Day of Victory over Nazism in WWII."

"Together we're moving towards a new victory!" he added.

The package features unspecified air defense systems and munitions as well as equipment to integrate Western systems with Ukraine's existing gear, which is mainly of Soviet vintage.

Ukraine's air defenses have played a key role in countering Russia's invasion, preventing Moscow's forces from gaining control of the skies and helping shield the country against missile and drone attacks.

- Anti-drone, artillery ammo -

Secret US documents from late February that were allegedly leaked online by a junior member of the Air National Guard detailed looming munitions shortages for Soviet systems that make up a significant chunk of Ukrainian medium and high-range protection.

Kyiv's international supporters have worked to bolster its existing defenses with a mix of cutting edge systems such as Patriot and NASAMS, as well as older equipment.

The package also includes ammunition for counter-drone systems meant to foil the threat of Iranian-made uncrewed aircraft that Russia has used for strikes in Ukraine, as well as 155 mm rounds -- a key type of artillery ammunition for Ukraine's forces.

It will also provide commercial satellite imagery services as well as support for training and maintenance.

The latest assistance brings total US military aid to Ukraine since Russia invaded the country in February 2022 to more than $36 billion.

The United States has spearheaded the push for international support for Ukraine, quickly forging an international coalition to back Kyiv after Russia invaded in February 2022 and coordinating aid from dozens of countries.

Kyiv has pushed for some items that its international supporters have been reluctant to provide, including Patriot air defense systems and advanced heavy tanks -- which were eventually delivered -- and others such as Western fighter aircraft, which have not been pledged so far.

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