Women soldiers could soon be allowed to serve in the Army for the first time in frontline close-combat fighting roles, Defence Secretary Philip Hammond has said.
Mr Hammond announced he was bringing forward a planned review on whether the bar on women joining the infantry and the Royal Armoured Corps should now be lifted.
The Defence Secretary said that he wanted to "send a message" that careers in the Armed Forces were fully open to women.
However a former head of the Army, Lord Dannatt, warned that the task of close-quarter fighting was "a role that is not for women".
The current head of the Army, General Sir Peter Wall, who will lead the review, said that the key issue in determining the outcome would be the "delivery of operational effectiveness".
The Ministry of Defence was already facing a requirement to review current policy on the deployment of women under EU equality laws by 2018.
But speaking at a Westminster lunch for political journalists, Mr Hammond said work on the review - which will also cover the Royal Marines and the RAF Regiment - would now begin immediately, with recommendations to be delivered by the end of the year.
"The image of the military is still a macho image - the last bastion of male chauvinism. The reality is very different," he said.
"But in the Army we still don't allow women in the combat arms - in the infantry and in the Armoured Corps. I think that at a time when the Americans, the Australians, the Canadians, even the French - the Israelis of course for years - have women in their combat arms, this is something we have to look at again.
"Not because there are thousands of women desperate to join the combat but because the message that the Army is not fully open to women who can meet the fitness and other requirements - the message that sends to women who might be looking to join other parts of the military.
"I am looking for a way forward that signals the Army's openness to all who can meet the standards required, maintaining combat effectiveness and militarily necessary standards of fitness."
Women already serve in a wide variety of combat roles across the forces including as fighter pilots, sailors and - most recently - submariners.
An MoD review in 2010 concluded that while women were "physically and psychologically" capable of the job of close combat, the effects of "gender mixing" on team cohesion were unknown and could have "far-reaching and grave consequences".
Mr Hammond acknowledged that the physical demands of close-combat fighting - with troops in Afghanistan required to carry loads of over 60 kilos on the battlefield - would limit the numbers of women who could do the job.
"We won't compromise on the fitness that we require for people to be able to keep themselves safe and to do their job effectively. That will obviously mean that some roles will have limited numbers of women who can meet those criteria," he said.
In a recent interview Sir Peter said that while admitting women to the infantry and other close-combat units would make the forces "look more normal to society", the issue needed to be handled with "great care".
In a statement following Mr Hammond's announcement, he said: "Our experience in Afghanistan has highlighted the increasingly important contribution women are making to operations.
"It is now sensible to review the Army's approach to the employment of female soldiers in the combat arms of the Army: the Royal Armoured Corps and the Infantry.
"The key factor informing this judgment will be the delivery of operational effectiveness".
However Lord Dannatt warned that while women were doing important work across the forces, they were not cut out for close-quarter combat.
"To be in a unit that is given orders to attack a hill, to attack a town, to attack a village, that is a role that is not for women," he told BBC News.
"If a woman is in a combat logistic patrol taking supplies forward, or is a medic on a foot patrol and gets caught up in fighting and does fantastically, that is tremendous.
"But that is a different set of circumstances from what I am describing. I think there is a point of principle there. I think it is an important one for people to reflect on."