More resources would be put into combating knife crime if extra funds were available, Metropolitan Police Commissioner Cressida Dick has said.
Ms Dick said she understood all public services were stretched but knew "exactly" where she would deploy any increased resources.
The commissioner said knife crime was beginning to stabilise in the capital and that moped-related crime was falling.
Asked about police numbers, Ms Dick told BBC Radio 4's Today programme: "All the public services are stretched. We are stretched.
"I think we need to focus on what matters most and, at the moment, violence on our streets is a big issue for Londoners.
"If you ask any police chief they will always want more resources, of course they will.
"I know exactly where I'd put them if I had more resources. And it would be into this issue."
Ms Dick said police actions were making an impact, stating: "We have got a lot of knife-carrying and we are bearing down very hard.
"We have taken thousands and thousands of knives off the streets.
"We are doing stop and search.
"We are doing it in an intelligent way and we are stopping and searching those people we know are prolific knife carriers."
The commissioner defended comments that short sentences for knife crime are not particularly effective.
Ms Dick said: "We should all be very proud of the reduction in the number of young people going into prison or custody.
"It's a huge reduction, 66%, I think over the last 10 years.
"I think that's a good thing.
"However, if somebody is going to go into custody because the public need to be protected, they are very violent.
"Then, I think, all research tends to suggest that short sentences are not particularly effective in terms of rehabilitation.
"It doesn't give a young person the chance to change their life in a short sentence, so that's all I was saying."