Metropolitan Police Commissioner Bernard Hogan-Howe says the operation is being reviewed, as there's "no doubt it's a drain."
has been living in the embassy since June 2012 to avoid extradition to Sweden, where prosecutors want to question him about 2010 allegations that he raped one woman and sexually molested another.
The Australian national has not been charged and denies the claims, saying he fears Sweden would extradite him to the United States, where he could face the death penalty if he is charged and convicted of publishing government secrets through WikiLeaks
On the operation to prevent Assange from fleeing the embassy, Hogan-Howe told LBC Radio that Metropolitan Police were looking at "how we can do that differently in the future, because it's sucking our resources in."
Asked if that meant fewer officers stationed around the clock outside the embassy, Hogan-Howe added: "We won't talk specifically about our tactics, but we are reviewing what options we have."
The cost of providing a constant police presence ready to arrest Assange should he emerge from the embassy in Knightsbridge, central London, is estimated at 10 million pounds, a Scotland Yard spokesman told CNN.
Assange has said the extradition warrant should be thrown out
because, in part, Swedish authorities refuse to interview him at the Ecuadorian Embassy, thereby prolonging a preliminary investigation that he says should have concluded long ago.
Assange rocketed to international fame when WikiLeaks began publishing secret government documents online.
After it published the procedures manual for the U.S. detention center at Guantanamo Bay, Cuba, in 2007, it posted documents related to U.S. activities in Iraq and Afghanistan, and diplomatic cables from U.S. embassies.