Speaking to BBC Radio 4’s Today programme in an interview to be broadcast on Saturday, Sir Keir said he had met the officers involved in the arrest.
He added that in the circumstances, you could understand why the officers would think they “need to do whatever we can to disable this guy”.
“There’s a guy on the ground, he’s got a rucksack on. And I don’t know what was going through the mind of those officers, but if I was there, I’d be thinking, he’s going to detonate something. He’s going to blow me up and everybody around here.
“In those circumstances, I think you can quite see why what could have gone through their mind is, we need to do whatever we can to disable this guy.”
Metropolitan Police Commissioner Sir Mark Rowley had accused the Green leader of amplifying “inaccurate and misinformed commentary”, in a letter to the politician sent out by the force on Thursday.
It is unusual for senior police leaders to publicly criticise politicians. It comes ahead of elections in Scotland, Wales and some English councils next week.
The Met has released footage from the officers’ body-worn cameras, in which they can be heard shouting repeatedly for the suspect to “get down on the ground” before he is Tasered, and then “drop the knife”.
It came after video shared on social media appeared to show the moment of the arrest, in which the officers can be seen kicking the man in the head several times in the struggle to wrest a knife from him.
Sir Mark went on to defend the officers’ actions in an interview earlier, saying their use of force had been “completely reasonable” in the circumstances.
In his statement, the Green leader said he had invited Sir Mark to “meet with me to discuss the police response and the wider issues raised in his letter”.
But he added: “Everyone in leadership has a responsibility for lowering the temperature at a time of such tension”.
“Police responses to emergency situations such as these do need later reflection in the right forums, but I accept that social media is not the appropriate channel for doing so”.
