WASHINGTON, July 6 (Reuters) - The United States plans to send cluster munitions to Ukraine to help it battle Russian invaders, US officials said on Thursday (Jul 6), a move opposed by human rights groups but which would provide a powerful new element to Ukraine's counteroffensive

A weapons aid package that includes cluster munitions fired by a 155mm Howitzer cannon was expected to be announced as soon as Friday, said three US officials speaking on condition of anonymity. The measure has been under serious consideration for at least a week, one of the officials said.

The White House said sending cluster munitions to Ukraine is "under active consideration" but it had no announcement to make. President Joe Biden is to attend a NATO summit next week in Lithuania expected to be dominated by the war in Ukraine.

Human Rights Watch called on Russia and Ukraine to stop using cluster munitions and urged the US not to supply them. The group said that both Russian and Ukrainian forces have used the weapons, which have killed Ukrainian civilians.

The munitions, banned by more than 120 countries, typically release large numbers of smaller bomblets that can kill indiscriminately over a wide area, threatening civilians. Bomblets that fail to explode pose a danger for years after a conflict ends.

A 2009 law bans exports of US cluster munitions with bomblet failure rates higher than 1 per cent, which covers virtually all of the US military stockpile. Biden can waive prohibitions around the munitions as Trump did in January 2021 to allow the export of cluster munitions technology to South Korea.

Ukraine has urged members of Congress to press Biden's administration to approve sending cluster munitions known as Dual-Purpose Conventional Improved Munitions (DPICM).