Prime Minister Gordon Brown has praised his Portuguese counterpart over his country's efforts to find missing four-year-old Madeleine McCann.
Madeleine disappeared while her parents were at a restaurant
Mr Brown thanked Jose Socrates for his government's work during a Downing Street summit.
Mr Brown said: "We are grateful to the Portuguese authorities for the time and effort and dedication that has been put into this investigation."
Madeleine disappeared in Praia da Luz, Portugal, on the evening of 3 May.
After the meeting, Mr Brown told reporters he had spoken to Madeleine's parents, Kate and Gerry, who had talked of their appreciation of the work of Portugal's police.
He said: "I thanked the Portuguese authorities for the work they have done to trace Madeleine McCann.
"I expressed the thanks of Madeleine's parents to the Portuguese authorities for their efforts and said we would do everything in our power to secure the safe return of Madeleine to her parents."
He added: "Obviously there are issues they want to be assured about and I have raised these with the Portuguese prime minister.
"He has assured me that everything that can be done will be done and obviously we look for progress in something that's heart-rending in its sadness, that a young child can be separated from her parents for so long."
Mr Socrates insisted that the case remained a high priority for his government.
He added: "It's important for Great Britain but it's important for Portugal, and it's very touching in public opinion in Great Britain but also in Portugal.
"Everyone in Portugal and the family knows we are doing our best."
Mr and Mrs McCann, of Rothley, Leicestershire, have based themselves in Portugal since their daughter's disappearance.
At the weekend, they spoke of their "considerable distress" at alleged plots to demand cash from them in return for bogus information.
A 39-year-old man has been arrested in the Netherlands accused of sending e-mails insisting they hand over 2m euros (£1.35m).
Prosecutors said the man, detained in Eindhoven, had confessed to making up the story about having information on Madeleine's whereabouts.
In Spain, an Italian man and Portuguese woman are accused of trying to extort money from the McCanns.
Neither they nor the man held in the Netherlands are being linked with the abduction of Madeleine.