Iran is planning to supply Russia with hundreds of weapons-capable drones for use in Ukraine, according to a top US official. Jake Sullivan, the White House national security adviser, said the information received by the US supported views that Russia’s heavy bombardments in Ukraine, which have led it to consolidate gains in the country’s east in recent weeks, were “coming at a cost to the sustainment of its own weapons”. “The Iranian government is preparing to provide Russia with up to several hundred UAVs [unmanned aerial vehicles], including weapons-capable UAVs, on an expedited timeline,” Sullivan said. “Our information further indicates that Iran is preparing to train Russian forces to use these UAVs, with initial training sessions slated to begin as soon as early July.” Sullivan said it was not clear whether Iran had delivered any of the drones to Russia yet. He noted that Iran’s drones had been used by the Houthi rebels in Yemen to attack Saudi Arabia. Drones have played a crucial role on both sides of the war in Ukraine, for everything from firing missiles from a distance, to dropping small bombs on targets, to conducting reconnaissance for artillery forces and ground troops. Ukraine’s forces have had particular success in using Turkish-made Bayraktar armed combat UAVs, and the US and other allies have supplied Kyiv with many types of smaller drones. “From our perspective, we will continue to do our part to help sustain the effective defence of Ukraine and to help the Ukrainians show that the Russian effort to try to wipe Ukraine off the map cannot succeed,” Sullivan said. Sullivan’s revelation comes on the eve of President Joe Biden’s trip to Israel and Saudi Arabia, where Iran’s nuclear programme and malign activities in the region will be a key subject of discussion. The US decision to publicly reveal that the two countries’ chief regional rival was helping to rearm Russia comes as both Israel and Saudi Arabia have resisted joining global efforts to punish Russia for its invasion of Ukraine due to their domestic interests. Russia’s grinding offensive in the east of Ukraine seems set to continue, despite fierce Ukrainian resistance emboldened by recent deliveries of western-supplied artillery, with the Ukrainian army warning that Russian troops were likely planning to launch some of their heaviest attacks yet in the Donetsk region. With no end to the fighting in sight, the Dutch prime minister, Mark Rutte, said during a visit to Kyiv that his country would supply Ukraine with more long-range artillery and an aid package worth €200m (US$201m). Western weapons – in particular precision, long-range artillery – were “already changing the course of the war,” the secretary of Ukraine’s National Security and Defence Council, Oleksiy Danilov, said on Monday.