As a dozen Occupy London protesters and local activists from the Save Leyton Marsh campaign in east London halt work at a site for a London 2012 venue by setting up a protest camp, a prominent campaigner is threatening that one phone call will see the size of group "escalate to whatever number is required".
The Olympic Delivery Authority (ODA), responsible for building Olympic Games venues in the capital, is constructing a temporary basketball arena on Leyton Marsh - green belt land - for athletes to practice on.
It will be pulled down in October.
Local residents who are part of the Save Leyton Marsh group called on Occupy London to help their campaign, which they say is about defending green belt land and local wildlife. They also pointed out how the money could have been better spent.
Occupy activists marched from Finsbury Square to the marshland and set up a small camp on the site, which has brought work to a standstill.
"It is a waste of money," Kris O'Donnell, an IT consultant who is part of the Occupy London group at Leyton Marsh, told IBTimes UK.
"The buildings are going to be up for five months. It is costing millions.
"What financial sense does that make? How about they upgrade the local school gyms?
"It could be so much better spent in the community helping the kids, instead of abusing a green belt area."
O'Donnell, who was one of the activists at Occupy's St Paul's encampment, said there has been no contact from the local authority, the London Borough of Waltham Forest, asking the group to leave.
"If the council is to speak to us, we will gladly speak to them, but there is a certain way these things should happen," he said.
"If it starts off negatively, then the process will end up being very, very slow. If they take the same route as the City of London Corporation did, then we will just sit on our hands.
"If they want more of us there, a quick phone call and we will escalate to whatever number is required."
While he is prepared to call in reinforcements, O'Donnell insisted that "this is 100 percent not a protest against the Olympic Games".
The group has reportedly been "mobbed" by local residents since its arrival, which has given fresh life to the Save Leyton Marsh campaign.
"The basketball training venue for the Olympics and Paralympics is a temporary structure that will be removed within a month of the end of the games and the land restored to its previous state," an ODA spokesman told the BBC.
"The vast majority of Leyton Marsh is completely unaffected."
Occuppy London has previously said that the Olympics are a "topic of interest", but that the group would only engage in protest activities when "it would not be obstructive".
Shadow Olympics Minister Tessa Jowell condemned the protest.
"I hope that those occupying Leyton Marshes and impeding the development of an Olympic and Paralympic practice venue will withdraw immediately to allow this essential work to go ahead," she said.
"The Olympics and Paralympics should not be disrupted by this action."