Education Secretary Ruth Kelly says she hopes the new school diplomas will be taken by most teenagers.
Many in education were disappointed by government plans
At a conference in London, heads of schools and colleges urged her to think again about having an over-arching diploma for England's qualifications.
Ms Kelly again rejected the idea of doing away with GCSEs and A-levels.
But she hoped the mainly vocational diplomas she has proposed would be "the choice of route for the majority".
The government disappointed many in education in February when it turned down the main plank of its own Tomlinson inquiry.
This was to subsume all existing qualifications - vocational and academic - into a new, four-tier diploma structure.
Instead it plans to phase in "specialised" diplomas in 14 subject areas or "lines of learning", such as engineering and health.
At the conference, members of the Association of Colleges, the National Association of Head Teachers and the Secondary Heads Association joined forces to urge the government to speed up the reform of education for 14 to 19-year-olds.
Ms Kelly said there were two main reasons for keeping GCSEs and A-levels as free-standing qualifications.
"First, because they are widely recognised and valued, in the education world and beyond.
"Our task is to establish more qualifications with that currency."
Secondly she was serious about the priorities she had set out, she said.
"As soon as anyone sets out to change GCSEs or A-Levels, that will inevitably become the focus of public, media and political attention - and that will inevitably drive the government's focus too."
She wanted the new specialised diplomas to be the basis for "the world-class system of mixed academic and vocational education that this country has lacked for so long".
She urged her audience to help to make them "a radical and popular choice for students".
Answering questions after her speech, Ms Kelly said she hoped that, in time, the diplomas "will come to be the choice of route for the majority of learners from the age of 14 onwards".
"It is our challenge to make sure that happens."
The head of the Qualifications and Curriculum Authority (QCA), Ken Boston, told the conference: "We must build a new form of qualification, which over the years will earn its spurs in the eyes of the learner, and those of employers and higher education."
But the general secretary of the Secondary Heads Association, John Dunford, said the key would remain the attitude of the top universities towards the qualifications achieved by those applying to them.
"If you have a premier qualification then people will always want to do it," he said.
"While A-levels are put on a pedestal, as they have been, a large number of young people will want to do them because they will be the access into the more prestigious universities.
"So the central question remains the extent to which A-levels are drawn into the diploma system. That remains our long-term objective."
A former education secretary, Estelle Morris, told BBC Radio 4's The World at One she also expected A-levels to go.
"I think maybe what the government has now is a sort of halfway house so that we are in an uneasy period where we are saying that you can equate success at A-level with success at some vocational subject," she said.
"Maybe that's OK for now but I don't think it will hold for long."
Liberal Democrat education spokesman Ed Davey has written to Ms Kelly asking her to clarify the government's intentions, about which he said many people were becoming increasingly confused.
He asked: "Is there any intention to broaden A-levels as the prime minister wants, before the 2008 review date? Has a decision been taken, but not announced, for a diploma system to replace A-levels by 2010?"