Border Protection Service officials will attempt to turn back two asylum seeker boats making the voyage to Australia - a move that could further inflame relations with Indonesia.
The West Australian understands Customs was yesterday moving to intercept two asylum boats on their way to Australian waters.
Australian officials have been instructed to turn or tow back the boats, if possible.
Indonesian leaders have repeatedly made clear their opposition to turn-back operations and expressed anger at revelations the Australian navy accidentally sailed into Indonesian waters recently.
The Government has thrown a curtain of secrecy over border protection operations and has so far refused to confirm that any vessels have been turned back since the coalition came to power.
But it is believed as many as six asylum boats may have been turned or towed back to Indonesia since the Government introduced its new hardline maritime regime - known as Operation Sovereign Borders.
Turn-backs or tow-backs can be dangerous operations, with asylum seekers sometimes willing to take desperate measures to avoid being forced back to Indonesia.
Defence Force Chief David Hurley, head of Operation Sovereign Borders Lt-Gen. Angus Campbell and Customs head Mike Pezzullo are due to appear before a Senate hearing today, with Labor and the Greens wanting to quiz them about the secrecy. The Senate voted last year to order Immigration Minister Scott Morrison to hand over documents detailing what instructions had been given to navy and Customs for intercepting asylum boats.
Senators will attempt to force officials to hand over that information and probe for details of recent turn-backs.
Documents released recently under freedom of information laws appeared to show navy and Customs heads decided among themselves after the Federal election that most inform ation about border security operations should be severely restricted.
But Mr Morrison said before the election he had made a decision to clamp down on information should he get into government.
Border Protection command is investigating how navy ships managed to accidentally sail into Indonesian waters during operations to intercept asylum seekers.
The Government boasted last week that no asylum seeker boats had arrived in Australia in five weeks.