A commemorative plaque will be installed at Westminster Bridge to remember the victims of the 2017 terror attack in which five people were killed.
Westminster Council said flowers will be placed at the scene to mark the anniversary, but that it would wait until Covid restrictions had been lifted to erect the official memorial.
Councillor Rachael Robathan, the leader of Westminster City Council, said that in the aftermath of such attacks people would not be “cowed by terrorism”.
Monday marks the fourth anniversary of the attack on March 22 2017, in which Khalid Masood drove a hire car into pedestrians on Westminster Bridge, before crashing into railings outside the Palace of Westminster.
He then stabbed Pc Keith Palmer, 48, to death before being shot dead by police.
Also killed in the atrocity were US tourist Kurt Cochran, Romanian tourist Andreea Cristea, 31, and Britons Aysha Frade, 44, and 75-year-old Leslie Rhodes.
An online event dedicated to the victims and their families will also take place on Sunday March 21.
Ms Robathan said: “Our thoughts are with the survivors as well as the family and friends who suffered loss following the terrorist attack at Westminster Bridge and New Palace Yard four years ago.
“Our communities can’t come together at the moment but in time, as Covid restrictions ease, we will meet to mark this tragic day.
“The aftermath of the terrorist attacks demonstrated that those who live and work in Westminster will not be cowed by terrorism, from whatever quarter it comes.
“We take the proper security measures with police, but as home to Parliament, Westminster is committed to being an open city and we refuse to have that tradition undermined by violence.”
She added that the council had submitted an application to put up the plaque, as the bridge is a Grade II* structure and planning permission is needed.
If approved, the memorial will be installed once Covid restrictions are lifted and will be placed on the top edge of the south parapet in the middle of Westminster Bridge.