WASHINGTON, March 3 (Reuters) - The United States announced a new military aid package for Ukraine on Friday worth $400 million primarily comprised of ammunition, but for the first time will include tactical bridges to move tanks and armored vehicles.

The bridges could be used by Ukrainian troops who have been training in "combined arms maneuver" warfare, which is the coordinated use of artillery shelling, alongside tank and armored vehicle attack movements, to retake territory seized by Russian forces since they invaded Ukraine a year ago.

The additional ammunition is being sent to help boost stocks in anticipation of a spring offensive.

"Assault bridging is essential for combined arms operations. It allows armored vehicles to cross narrow rivers and ditches that would otherwise cause a whole force to slow down," said Jack Watling, a Senior Research Fellow for Land Warfare at the London-based Royal United Services Institute.

"Importantly, assault bridges are only critical for offensive operations showing that the US is preparing Ukraine to continue retaking its territory," Watling added.

In January, Germany agreed to send Leopard tanks to Ukraine and said it would work with allies to send more. German aid for Ukraine was expected to be a major topic when U.S. President Joe Biden and German Chancellor Olaf Scholz met at the White House on Friday. Several NATO allies have pledged a range of armored fighting vehicles.

"This military assistance package includes more ammunition for U.S.-provided HIMARS and howitzers, which Ukraine is using so effectively to defend itself, as well as ammunition for Bradley Infantry Fighting Vehicles, Armored Vehicle Launched Bridges, demolitions munitions and equipment, and other maintenance, training, and support," Secretary of State Antony Blinken said in announcing the aid.

Anatoly Antonov, Russia's ambassador to Washington, said the U.S. wanted to inflict a strategic defeat on Moscow but had no chance of succeeding, TASS news agency said.

"All foreign weapons that fall into Ukrainian hands on the battlefield will be ground up and destroyed," TASS quoted Antonov as saying.

The package will be funded using Presidential Drawdown Authority, or PDA, which authorizes the president to transfer articles and services from U.S. stocks without congressional approval during an emergency, Blinken said.

Overall, the United States has provided nearly $32 billion in aid to Ukraine to defend itself against Russia, which invaded its pro-Western neighbor on Feb. 24 last year.