Christians will be among the demonstrators who will call for an immediate ceasefire in Lebanon during the event.
The marching route will see them pass the US embassy in London’s Grosvenor Square.
The demonstration has been organised by a number of groups including the Stop the War Coalition and the British Muslim Initiative.
Lindsey German, convenor of STWC, predicted that tens of thousands of people would travel to the capital to join the protest."We are expecting a huge turnout because the British public is genuinely appalled at the events in Lebanon." she said.
"People want an immediate ceasefire which respects Lebanon's borders."
The march will be followed by a rally featuring a number of speakers including anti-nuclear campaigner Walter Wolfgang, 83.
Prime Minister Tony Blair delayed his summer holiday plans as he continues with efforts to resolve the Lebanon crisis. He had been due to join his family in the Caribbean for a three-week break.
Hopes were raised Friday that a UN resolution to bring an end to hostilities in the Middle East would soon be agreed.
The US and France were closer to finding agreement on a draft text after several hours of talks between US Ambassador John Bolton and French Ambassador Jean-Marc de la Sabliere.
US Secretary of State Condoleezza Rice also expressed her support for an immediate ceasefire in Lebanon as a first step in resolving the crisis – an indication the Bush administration may be willing to move closer to the position of many European countries in a bid to overcome the diplomatic stalemate.
