WASHINGTON, July 18 (Reuters) - The United States will announce a new pledge to buy $1.3 billion worth of military aid for Kyiv in its conflict with Russia in the coming days, two U.S. officials said.

The previously unreported weapons package includes air defenses, counter-drone systems, exploding drones and ammunition, one of the U.S. officials said.

The United States is using funds in its Ukraine Security Assistance Initiative (USAI) program, which allow President Joe Biden's administration to buy weapons from industry rather than pull from U.S. weapons stocks.

Among the systems and ammunition the U.S. plans to buy for Kyiv are counter-air defenses made by L3Harris Technologies called the Vehicle-Agnostic Modular Palletized ISR Rocket Equipment or VAMPIRE, one of the officials said.

Also included are two different types of loitering munitions, the Phoenix Ghost drone made by AVEVEX, a private company in California, and the Switchblade, made by AeroVironment Inc.

Additionally, a person briefed on the matter said Ukraine will get a significant number of counter-drone systems made by Australia's DroneShield Ltd alongside radars, sensors and analysis systems.

The U.S. Department of Defense's impending announcement of the security assistance to Ukraine comes alongside a virtual meeting on Tuesday of the Ukraine Defense Contact Group, a gathering of allies assisting Kyiv as Ukraine presses its counteroffensive against Russian invasion forces.

Delivery of the weapons and systems depends on their availability and production timeline. The contents and value of the package may also change up until the announcement.

The Pentagon has provided more than $10.8 billion in security assistance for Ukraine under the USAI in fiscal 2023, in seven separate tranches. The planned package would be the eighth. In the fiscal year that ended Sept. 30, 2022, Washington put $6.3 billion worth of USAI funds to work buying for Ukraine's defense. (Reporting by Mike Stone in Washington Editing by Don Durfee and Angus MacSwan)