British detectives investigating the disappearance of Madeleine McCann are poised to stage operations on Portuguese soil.
Investigators from Scotland Yard are waiting for an official agreement later this week, and hope to begin "operational activity" linked to the case in the near future.
Deputy Assistant Commissioner Martin Hewitt said he is "cautiously optimistic" that Portuguese and British officers can act soon.
He said: "I am cautiously optimistic that in the not-too-distant future we are going to start to see activity."
Mr Hewitt would not reveal what the operations will involve.
Police also revealed that they are now looking at five more cases in which young British girls were sexually assaulted during holiday home break-ins by a lone intruder in the Algarve.
One of these was in 2005 on a 10-year-old girl in Praia da Luz, where Madeleine, then three, vanished two years later.
Scotland Yard made public appeals to try to trace the paedophile last month, and so far more than 500 people have made contact with information.
Officers are now looking at a total of nine sexual assaults and three "near misses" on British girls aged six to 12 between 2004 and 2006.
Last month the team revealed that they were looking at a series of break-ins, including two burglaries in the town where Madeleine disappeared.
Detective Chief Inspector Andy Redwood said today: "As a result of those 500 calls, we have now identified a further five sexual assaults and one near miss. None of those six matters we were aware of prior to our appeal.
"In this new tranche of information we have got one crime which is very clearly in the heart of Praia da Luz in 2005, on a young, white, 10-year-old girl.
"Clearly the fact that we've now got an assault that is in the heart of Praia da Luz, very close to where a previous matter had been reported, means that we are even more interested in this as part of the inquiry."
British detectives launched a fresh investigation into Madeleine's disappearance in July last year - two years into a review of the case.
After shelving their inquiry into Madeleine's disappearance in 2008, Portuguese authorities said last October that a review had uncovered enough new information to justify reopening it.
Portugal has declined to set up an official joint investigation with the Met.
Mr Hewitt said Prime Minister David Cameron and Home Secretary Theresa May have expressed a personal interest in the case, and stand ready to intervene to press the Portuguese authorities for help if necessary.
British investigators are looking at 18 potentially-linked break-ins in the area, where little or nothing was stolen.
This includes the nine sexual assaults, three near-misses and six incidents where the intruder was disturbed before anything happened.
In the previous appeal, the suspect was described as a tanned, dark-haired man who spoke English slowly, with a foreign accent and possibly slurred speech, had unkempt hair and was unshaven, and smelled strange. Some witnesses said he had a pot belly.
There is a £20,000 reward for information leading to the arrest and prosecution of those responsible for Madeleine's disappearance.
Anyone with information can call police on 0207 321 9251 or Crimestoppers anonymously on 0800 555 111.