Israel and Hamas reached a four-day truce under which 4 detainees were released on Friday, but the British-based Palestine Solidarity Campaign, which organises today's march, said the truce was "just a short and partial respite for the people of Gaza."
Egyptian security sources said Hamas was expected to release 14 more detainees on Saturday, as Israel prepares to release 42 Palestinian prisoners on the second day of the truce.
The Palestine Solidarity Campaign called for a permanent cessation of the conflict in the Gaza Strip.
Lindsay German, an anti-war activist who has announced her intention to take part in the march, told Sky News: "We want a permanent ceasefire that can then lead to a political solution. We are very far from that and our government needs to do more to ensure that happens."
Police said on Friday they would deploy more than 1500,<> security personnel this weekend to control the protest.
"We continue to see the cumulative impact of continued protest, increased tension and increased hate crimes," said Adi Adelkan, deputy assistant commissioner of the Metropolitan Police, adding that police would distribute leaflets to protesters warning them of penalties for racist behaviour.
"This states that anyone who exhibits racist behavior or incites hatred against any group should expect to be arrested, as should anyone who supports Hamas or any other banned organization."
More than 120 demonstrators were arrested during a march earlier this month when skirmishes broke out between police and far-right groups that had gathered to protest the demonstration.