The US State Department announced the approval Thursday of the sale of $650 million worth of air-to-air missiles to Saudi Arabia to help the country protect itself from drone attacks.

The approval will allow the Saudis to buy up to 280 of the AIM-120C advanced medium-range missiles and related equipment, replenishing an existing supply of the missiles, the department said.

A State Department spokesperson said the Saudis have already been able to use the missiles to intercept unmanned aircraft that threatened both Saudi and US forces inside the country, mainly from Yemen.

"We've seen an increase in cross-border attacks against Saudi Arabia over the past year," the spokesperson said.

The Saudis are leading a fight against the Houthi rebels in Yemen, who are supported by Iran.

US officials say the Iranians have supplied the Yemenis with drones and drone technology.

The sale comes as President Joe Biden's administration takes a cautious approach to supporting the Saudis, out of concern over their harsh tactics towards the Houthis as well as human rights violations.

The State Department spokesperson stressed that the missiles cannot be used against ground targets.

The sale of the missiles "is fully consistent with the administration's pledge to lead with diplomacy to end the conflict in Yemen while also ensuring Saudi Arabia has the means to defend itself from Iranian-backed Houthi air attacks," the official said.