US sends mines to Ukraine to help slow Russian advance

The Biden administration will give Ukraine antipersonnel mines to help it slow Russia's battlefield advances, marking the second major shift on US military support for Kyiv in days.

After allowing Ukraine to use longer-range American missiles to launch strikes deeper into Russia, US Defense Secretary Lloyd Austin said the shift in Washington's policy on antipersonnel landmines for Ukraine was needed to counter changing Russian tactics.

The war, which reached its 1000-day milestone on Tuesday, has largely been going Russia's way.

Moscow's bigger army is slowly pushing Ukraine's forces backward in the eastern Donetsk region, while Ukrainian civilians are being maimed and killed by Russian drones and missiles often fired from inside Russia.

Individual ground troops, rather than forces more protected in armoured carriers, were leading the Russian battlefield advance, so Ukraine had "a need for things that can help slow down that effort", Austin said on Wednesday during a trip to Laos.

The announcement comes two months before Donald Trump replaces Joe Biden in the White House.

Trump has pledged to swiftly end the war and has criticised the amount the US has spent on supporting Ukraine.

Biden administration officials say they are determined to help Ukraine as much as possible before he leaves office, and they announced on Wednesday the US intended to cancel half of the debt - some $US4.6 billion ($A7.1 billion) - Ukraine owed to the country.

The steps taken to help Ukraine are likely to vex Moscow.

Humanitarian groups have long criticised the use of antipersonnel mines because they present a lingering threat to civilians.

Amnesty International called the US decision "reckless" and a "deeply disappointing setback".

Norway's foreign minister, Espen Barth Eide, called it "very problematic" because Ukraine was a signatory to an international convention opposing the use of landmines.

Austin pointed out that Ukraine already made its own antipersonnel mines, and the US had been providing Ukraine with anti-tank mines.

He said the new mines were not persistent, meaning troops could control when they would self-detonate.

"That makes it far more safer eventually than the things that they are creating on their own," Austin said.

The mines are are electrically fused and powered by batteries so they will not detonate when the battery runs out.

Russia already uses landmines in Ukraine, but those do not become inert over time.

Ukraine assured the US it would use the mines in its own country and would not put them in civilian populated areas, according to a US official.

The mines are contained in a $US275 million package of new military assistance announced by the Biden administration on Wednesday.

Also included are High Mobility Artillery Rocket Systems, or HIMARS, as well as 155mm and 105mm artillery rounds, Javelin anti-armour munitions, and other equipment and spare parts.