The UK-wide Palestine Solidarity Campaign has encouraged protestors to convene at noon in Hyde Park, for a march to the US embassay at Nine Elms, on the south side of the Thames.
The call has been re-tweeted by the Londonderry branch of the Ireland Palestine Solidarity Campaign (IPSC).
Meanwhile, there are a handful of gatherings planned in Ireland on Remembrance Day, almost all of them in the Republic.
The online flyer promoting the London march bears the message: "Ceasefire now!"
However, on Monday night, the Met asked organisers to reconsider.
Deputy Assistant Commissioner Ade Adelekan said: "The risk of violence and disorder linked to breakaway groups is growing.
"This is of concern ahead of a significant and busy weekend in the capital.
"Our message to organisers is clear: Please, we ask you to urgently reconsider. It is not appropriate to hold any protests in London this weekend."
The Royal British Legion is encouraging the public to observe the traditional two-minute silence at 11am on Saturday, with acts of remembrance expected "at war memorials and in public places throughout the UK and Commonwealth".
Meanwhile, the legion is hosting two performances of its "Festival of Remembrance" on Saturday at the Royal Albert Hall... right next to Hyde Park, where the demonstration begins.
The first performance of the day is at 2pm with doors opening at 12.30pm. The evening performance is at 7pm, with doors at 5pm.
In Dublin on Saturday, protestors are asked to gather at The Spire near the GPO at 1pm.
There will be a rally at 7pm in The Diamond, Bellaghy, south-east Co Londonderry.
A documentary screening about Gaza will take place at Moville, north-east Donegal, at 2.30pm at St Eugene's Hall.
There will be a vigil at 1pm in Limerick's Bedford Row.
In Cork, there will be a march beginning at 1pm in Grand Parade.