US President Donald Trump is hosting the NATO chief in Washington on Monday after teasing a "major statement" on Russia's war in Ukraine, with senior Republicans preparing an arsenal of sanctions against Moscow.

The White House has U-turned from an announcement earlier this month that it would pause some arms deliveries to Kyiv, instead announcing a new deal which would involve NATO purchasing some US weapons to send to Ukraine.

If the plan is finalized, it would allow critical aid to flow to Ukraine as it endures one of Russia’s heaviest assaults of the war.