"We are turning up the heat in every way we possibly can," Ottawa Police Chief Peter Sloly told reporters.
"We are asking for a major push of resources to come in the next 72 hours."
The "Freedom Convoy" consisting largely of truckers began as a movement against a Canadian vaccine requirement for cross-border drivers.
But it has since evolved into a rallying point against Prime Minister Justin Trudeau's strict measures to fight the pandemic.
This weekend, police counted 1000 trucks and 5000 protesters, down from 3000 trucks and 10,000 to 15,000 protesters last weekend, Sloly added.
Ottawa awoke to its second week of what its political and policing leaders now describe as a siege with Sloly saying the occupation has gone beyond anything he can adequately deal with.
The protests have been largely peaceful.
A short stretch of Metcalfe Street in downtown Ottawa, home to Canada's parliament, central bank and buildings including Trudeau's office, smelled of campfire on Monday.
A clustering of trucks, cars and tractors without trailers bore signs deriding everything from vaccines and mandates to Canada's carbon tax.
One sign showed a poster of Canada's Charter of Rights and Freedoms, which guarantees rights including that of life, liberty and security of the person - subject to "reasonable limits."
Packets of water bottles, briquettes and diapers were piled high beside open-sided white tents with tables of food.
There was also evidence of pushback from residents.
Small signs in the ground-floor windows of an apartment building a few blocks away said: "GO HOME MORONS" and "VACCINES SAVE LIVES".
The Canadian government, which has refused to back down on the issue, will hold a news conference on Monday afternoon to discuss the blockade.
Trudeau, who is isolating after testing positive for COVID-19, will not attend.
Trudeau and his family left their downtown home after truckers started arriving in Ottawa and his location has not been disclosed due to security concerns.
Late night honking and occasional fireworks have disrupted the normally quiet life of the residents in downtown Ottawa.
An Ottawa court will hear an application for an injunction to end the loud honking downtown residents say has become incessant and unbearable.
Lawyer Paul Champ, who represents the plaintiffs, told Reuters on Sunday he expects the police to enforce "to some extent" an injunction if the court grants it.
On Sunday night, police began removing gas and fuel supplies at a logistics encampment set up by protesters after the city's mayor declared a state of emergency on Sunday.
A well-organised supply chain - including portable saunas, a community kitchen and bouncy castles for children - has sustained the protesters.
It has relied partly on funding from sympathisers across Canada and the United States, police said.
Canadians have largely followed government's health measures and nearly 79 per cent of the eligible population has taken a double dose of the vaccine.
But recent polls suggest frustrations against restrictions are growing.
