Australian soldiers will be deployed to assist an increasing team of Australian police officers investigating the downing of Flight MH17.



Prime Minister Tony Abbott said details were being finalised to determine how many armed troops would be on the ground, as the number of Australian Federal Police deployed rose.



Mr Abbott said a further 100 Australian Federal Police officers would fly to London today to join the 90 already in Europe to bolster Australia's contribution to a multi-national commitment to the MH17 investigation.



The latest increase in officers brings the total to more than 200 Australian government officials working abroad to bring the remains of the dead home.



"This is a humanitarian mission with a clear and simple objective, to bring them home," Abbott said. "All we want to do is to claim our dead and to bring them home."



It is the largest overseas mission by the AFP since the Bali bombings.



"Our objective is that the remains can be recovered, that the investigation can go ahead and that justice can be done. That is the sole objective of the Australian government," he said from AFP headquarters today.



"There are currently 90 Australian Federal Police personnel deployed to Europe to participate in the international police mission that is now being planned.



"Ukraine has formally delegated to the Dutch leadership of all aspects of the investigation that is taking place.



"Australia is close to finalising an agreement with Ukraine for the deployment of Australian police - some of whom will be armed.



"A further 100 AFP will be leaving for Europe today."



Mr Abbott held further talks with US president Barack Obama today, on securing access for investigators to the MH17 air crash site, as a multi-nation coalition of police officers has begun to take shape.



In the telephone call this morning, Mr Obama thanked Mr Abbott for Australia's leadership and willingness to send both investigators and federal police into the Ukraine.



They agreed on the need for a "full, unimpeded and transparent" international investigation and secure access to the site for investigators.



A White House spokesman said the president had said the US would co-ordinate closely with Australia, including in the UN Security Council, as the issue progressed.



Overnight, foreign minister Julie Bishop and her Dutch counterpart Frans Timmermans signed a memorandum of understanding with their Ukrainian counterpart Pavlo Klimkin which officially put the Netherlands in charge of the crash investigation.