WASHINGTON — The Pentagon announced the U.S. is sending another $800 million in aid to assist Ukrainian forces that includes cluster munitions as U.S. officials on Friday defended providing Ukraine the controversial weapon to help their attack on entrenched Russian troops.

The new military aid also includes 64 Stryker and Bradley fighting vehicles, air-defense missiles and anti-mine equipment.

Jake Sullivan, national security adviser to President Joe Biden, left the formal announcement Friday to the Pentagon about sending cluster munitions to Ukraine. But he acknowledged during a White House briefing that this has been a difficult decision and defended the use of the weapon as Ukraine is running out of artillery rounds and Russian forces have been using cluster bombs since the beginning of the war.

“Ukraine would not be using these munitions in some foreign land,” Sullivan said. “This is their country they’re defending. These are their citizens they’re protecting and they are motivated to use any weapon system they have in a way that minimizes risks to those citizens.”

The announcement comes as Ukrainian forces struggle to break through Russia’s front line during a counteroffensive that began last month. There is a growing sentiment among Western officials that Ukraine needs to seize on the summer weather, conditions on the ground and any impact that the short-lived revolt last weekend by Russian mercenary forces might have done to its military cohesion.

But Army Gen. Mark Milley, chairman of the Joint Chiefs of Staff, last week dismissed concerns that Ukraine’s counteroffensive is moving too slow. He said he thought the initial campaign would take six weeks to 10 weeks.

“It’s going to be very difficult. It’s going to be very long,” he said June 30 at the National Press Club in Washington. “No one should have any illusions about any of that.”

Milley also said the U.S. has been thinking about providing the munitions "for a long time." He said Ukrainian forces already have used cluster bombs received from other countries.

"The Ukrainians have asked for it, other European countries have provided some of that, the Russians are using it," he said.

Cluster munitions are weapons that break open in the air and disperse smaller bomblets across a large stretch of area when detonated. Proponents of banning cluster bombs contend they kill indiscriminately and endanger civilians long after their use. The Human Rights Watch, an international advocacy group, published a report on Thursday that said both sides have used cluster munitions that have killed Ukrainian citizens and urged the U.S. not to supply them.

More than 100 countries signed the Convention on Cluster Munitions in 2008, which bans the use, production or stockpiling of these munitions. Russia, Ukraine and the U.S. did not sign the treaty.

Colin Kahl, undersecretary of defense for policy, said Friday that the U.S. would only be providing cluster munitions with a failure rate, or “dud rate,” of less than 2.35%. Munitions with a reduced “dud rate” means there will be far fewer unexploded rounds that can result in unintended deaths of civilians. Congressional restrictions prohibit the U.S. from selling or transferring cluster munitions with dud rates more than 1%.

But Kahl said the Biden administration is not breaking the law. The president has the authority to waive that requirement on national security grounds and that is what he did with this military aid for Ukraine, since the counteroffensive “has been hard sledding.”

“The Russians had six months to dig in. Those defensive belts that the Russians have put in place in the east and the south are hard,” Kahl said. “They would be hard for any military to punch through. We want to make sure that the Ukrainians have sufficient artillery to keep them in the fight. Because things are going a little slower than some had hoped. There are very high expenditures of artillery.”

The cluster munitions that the U.S. will provide are more modern ones that went through tests conducted by the Defense Department between 1998 and 2020. Kahl said the U.S. dud rate is much lower than Russia’s cluster bombs, which have a rate of 30 to 40%. He also said he is confident in how they will be used by Ukraine.

“The Ukrainian government has offered us assurances in writing on the responsible use of [cluster munitions], including that they will not use the rounds in civilian, populated urban environments and that they will record where they use these rounds to simplify later demining efforts,” Kahl said.

Cluster munitions can be launched from High Mobility Artillery Rocket Systems, or HIMARS, and 155mm howitzers, which the U.S. has provided to Ukraine in more than $41.3 billion in security assistance since the war began in February 2022.

This is the 42nd time that the U.S. has provided weapons through the presidential drawdown authority, which means it will come directly from Pentagon stocks and be sent quickly on an emergency basis. Aid given this way typically means it reaches Ukraine in a matter of weeks.

The list of weapons and items in the latest aid include:

• Additional munitions for Patriot air defense systems.

• AIM-7 missiles for air defense.

• Stinger anti-aircraft systems.

• Additional ammunition for High Mobility Artillery Rocket Systems.

• 31 155mm howitzers.

• 155mm artillery rounds and 105mm artillery rounds.

• 32 Bradley Infantry Fighting Vehicles.

• 32 Stryker armored personnel carriers.

• Mine-clearing equipment.

• Tube-launched, optically tracked, wire-guided missiles.

• Javelin and other anti-armor systems and rockets.

• Precision aerial munitions.

• Penguin Unmanned Aerial Systems.

• 27 tactical vehicles to recover equipment.

• 10 tactical vehicles to tow and haul equipment.

• Demolitions munitions and systems for obstacle clearing.

• Small arms and more than 28 million rounds of small arms ammunition and grenades.

• Spare parts and other field equipment.

previous coverage

• More US allies hit mark for defense spending in 2023, NATO chief says
• Ukraine nuclear tensions spike with US Air Force radiation detector ready