The US is planning to send Ukraine a cluster munitions package to help in its counteroffensive against Russia, US media reports.

Ukraine has been asking for the weapons for months amid an ammunition shortage.

Cluster munitions - which are banned by more than 100 countries - are a class of weapons that contain multiple explosive bomblets called submunitions.

The Biden administration is expected to announce the package on Friday, the BBC's US partner CBS News reports.

US officials had reportedly been hesitant to supply Ukraine with cluster munitions as they can kill indiscriminately over a wide area, threatening civilians. The US has a stockpile of these cluster bombs, which were first developed during World War II.

The munitions are controversial because of their high failure rates, meaning unexploded bomblets can linger on the ground for years and possibly detonate later on.

US law prohibits the transfer of cluster munitions with bomblet failure rates higher than 1% - meaning more than 1% of the bomblets in the weapon do not explode - but President Joe Biden is able to bypass this rule.

Defence Department officials told reporters on Thursday the Biden administration was considering sending cluster munitions with a failure rate lower than 2.35%.

The Pentagon noted that Russia has already been using cluster bombs in Ukraine with even higher failure rates. A United Nations investigation found Ukraine has likely used them as well, though the country has denied doing so.

Officials are planning to send artillery shells to Ukraine, with each containing 88 separate bomblets, according to US media reports. They would be fired from Howitzer artillery weapons already deployed by the Ukrainian army.

The aid package also includes Bradley and Stryker fighting vehicles, air defence missiles and anti-mine equipment, officials told reporters.

Human rights groups have urged Russia and Ukraine not to use cluster munitions and have asked the US not to supply them.

Some US lawmakers have also asked the Biden administration not to send the weapons, arguing their humanitarian costs outweigh their benefits in the battlefield.

Defence Department official Laura Cooper told Congress last month that military analysts had found that cluster bombs would be "useful, especially against dug-in Russian positions".

The Biden administration's new weapons package is worth $800 million (£626,500), CBS News reported.