Election 2015: No Wales powers bill in first 100 days
A new law giving Wales more powers may not be introduced as quickly as had been suggested by the chancellor.
BBC Wales understands the proposed Wales Bill will not be among the early laws to be debated by MPs.
During the general election campaign, Chancellor George Osborne promised Welsh legislation within 100 days of the Conservatives taking power.
On Tuesday, First Minister Carwyn Jones warned "it would be extraordinary if the promise were not kept".
In First Minister's Questions, he added "the people of Wales would find that difficult to accept".
David Cameron has told Mr Jones he expects a new law to give Wales more powers to be included in the Queen's Speech at the state opening of parliament later this month.
But this does not necessarily mean MPs will get to debate the new legislation as quickly as suggested during the general election campaign.
UK ministers have said they want to get the detail of any new law right, rather than meet an artificial deadline.
A pledge to ensure Welsh public spending remains higher per head than in England could be met without legislation.
The prime minister announced in February plans to give the Welsh assembly more powers over energy projects, its own elections and scope for borrowing on the financial markets.
On Tuesday, Welsh Secretary Stephen Crabb said: "I think it's really important to show momentum. I think it's really important that we show to Wales that we're going to follow through on our promises and our commitments and right at the heart of that is a commitment to deliver fair funding for Wales.
"But it's also really important that we take time to get the detail right.
"Wales has suffered in the past by having devolution legislation that's been badly written or vaguely written.
"That's what's led to Welsh government and UK government fighting it out in the courts."
Responding, Mr Jones said there was "much talk of rowing back on the promise that was given".
"We have to wait and see, but it would be extraordinary if the promise to move forward with further devolution in Wales was not kept, and broken within a week of the government coming into power," he said.
"I think the people of Wales would find that very difficult to accept, to see a promise broken that quickly. But let's wait and see."
Later, Welsh Liberal Democrat leader Kirsty Williams said the "dithering" over further Welsh powers was "shameful".
"This revelation, if true, just confirms what we already knew: the Liberal Democrats were the sole driving force behind devolution in the last government."
Plaid Cymru leader Leanne Wood said people in Wales "voted overwhelmingly in favour of pro-devolution parties and opinion polls show that there is an appetite to take more responsibility over our own affairs".
"It is therefore wrong for the UK government to try to stifle this," she said.