New powers will be devolved to Wales under "landmark" plans being announced by David Cameron and Nick Clegg ahead of Sunday's St David's Day celebrations.
Funding reforms, more energy powers and constitutional changes are set to be detailed in a paper to parliament.
But the devolution package for the Welsh Assembly is not expected to include proposals for handing over controls of policing and welfare.
Ahead of a visit to Wales, the Prime Minister said: "This is the latest step in finding lasting settlements across the country to make our United Kingdom stronger and fairer.
"We are delivering on devolution in every part of the UK.
"We want to deliver new powers to Wales so that more decisions are taken closer to the people and give greater responsibility to the Welsh Assembly.
"That means those who spend taxpayers' money must be more responsible for raising it.
"This is devolution with a purpose, working for Wales."
It comes after months of negotiations, led by Welsh Secretary Stephen Crabb, who is himself a Scot, between party leaders in Westminster and Cardiff Bay.
Reforms aimed at addressing issues about the way the assembly is funded are expected to be outlined, along with changes intended to remove perceived barriers preventing a referendum being staged on income tax powers.
Constitutional changes that would allow the assembly to become a permanent parliament with the ability to draw up its rules, are also set to be announced.
But cross-party talks failed to reach an agreement on transferring responsibility for police, courts and prisons, or the benefit system.
The Deputy Prime Minister said: "I've been banging the drum for years now for greater devolution for Wales, and the rest of the United Kingdom.
"So I am delighted to be coming to Wales to announce this new constitutional settlement, another landmark on the journey of decentralisation.
"Putting real power into the hands of the Welsh people is a vital part of creating a stronger economy in a fairer society for everyone.."
Mr Crabb said: "This is a strong package that creates the foundations for a stronger, fairer, lasting devolution settlement for Wales.
"These new powers create an important opportunity for Wales, they are powers with a purpose.
"As a UK Government, we believe in rebalancing the economy to enable wealth to be created more fairly and evenly across the whole country.
"This St David's Day package provides a toolkit to help strengthen the economy here in Wales too."
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