He told BBC Radio 4's Today programme that the UK would now work with those nations to coordinate how the military aid is delivered and "put into Ukrainian hands" - but gave no further details.
He said that the Kremlin was likely to be "reflecting" on the stiff Ukrainian resistance it was meeting and conceded that there was a risk it would resort to heavier bombardments on Ukraine to compensate.
And he said British diplomatic efforts were continuing to persuade other countries to agree to have Russia removed from the Swift international bank transfer system.
"It's not a unilateral decision the UK can take - but our position is clear," he said.
