Sadiq Khan plans to write to Amber Rudd, the Home Secretary, urging her to make supporting all factions of Hezbollah illegal in Britain.
Both Conservative and Labour figures have lobbied for a ban on the political wing of the terror group. Its official terrorist wing is already proscribed in this country.
Mr Khan's expected letter comes after Hezbollah flags were spotted at last month's Al-Quds march in central London.
Mr Khan said: "I share the concerns of the Jewish community about support shown for Hezbollah, which is an illegal, proscribed and antisemitic organisation.