The Turkish opposition is firmly against allowing US or other military forces to operate from Turkish soil.
But the governing Justice and Development Party has an overwhelming majority in parliament.
The BBC's Jonny Dymond in Istanbul says many observers believe deputies will back the ruling party's leaders.
He says the government - which resisted US pressure for months - is bowing to the inevitable.
Turkey already hosts some 50 US aircraft that patrol a no-fly zone over northern Iraq.
If Turkey withheld support for the US, it might suffer all the consequences of war in Iraq without getting any help from Washington during or after the conflict, our correspondent says.
Turkey, a Nato member, has a 330-kilometre (200-mile) border with Kurdish-controlled northern Iraq.
The US and allies such as Britain have been pressing Turkey for months to grant access to its land and air bases.
A number of high-level officials - including the US chairman of the Joint Chiefs of Staff, General Richard Myers, and UK Defence Secretary Geoff Hoon - have visited Ankara to press their claim.
No explicit call
The latest move in Turkey came after a meeting of the influential National Security Council, which brings together the country's powerful generals and political leaders.
It urged the government to win parliamentary approval for "military measures" if war breaks out in neighbouring Iraq, but stopped short of an explicit call to open air bases to US forces.
Turkey has been deploying its own forces towards its border with Iraq.
Parliament is likely to meet next week to discuss the measures.