Iran has indicated repeatedly that it plans to re-examine relations with London.
Meanwhile in Berlin, Angela Merkel, the German chancellor, said on Monday that Germany would be preparing possible further sanctions against Iran in the weeks ahead if there was no change in its disputed nuclear energy programme.
In a joint news conference in the German capital with Binyamin Netanyahu, the Israeli prime minister, Merkel said: "Germany has made clear that if Iran's reaction does not change, we will be working on a comprehensive package of sanctions.
"Of course we would prefer it if these [sanctions] could be agreed within the framework of the United Nations Security Council."
Netanyahu said the time had already come to apply "crippling sanctions" against Iran over its nuclear programme, which is says the country is developing for hostile purposes.
"If we don't apply sanctions, crippling sanctions against this Iranian tyranny, when shall we apply them? If not now, when? The answer is now," he said.
Tehran says its nuclear work is aimed only at generating electricity for civilian purposes.
Israel, assumed to be the Middle East's only nuclear power, sees Iran's project as a threat to its existence, citing hostile rhetoric against the Israel by Iranian leaders.
Earlier, Netanyahu and members of his government took part in a special joint session with the German government in Berlin, a symbolic visit highlighting the two nations' bond six decades after the Holocaust.
The historic trip was originally scheduled for late November, but was put off at the last moment when Netanyahu fell ill.