A decision on whether to build a £1.4bn M4 relief road in south Wales is now expected to be announced in early June, First Minister Mark Drakeford has said.
Mr Drakeford had already suggested the news could be delayed until after European elections, due on 23 May.
In a statement on Tuesday, he said he had been considering carefully an inspector's report on the project.
There are calls for the plans to be scrapped, after a Welsh minister declared a "climate emergency".
The 14-mile (23km) six-lane motorway would be built south of Newport, between Magor and Castleton, to relieve congestion around the Brynglas Tunnels.
In a written statement to AMs on Tuesday, Mr Drakeford said: "Members will be aware that I have been considering carefully the inspector's report and advice from officials on the M4 Project.
"I anticipate that I will be in a position to announce my decision on whether or not to make the legal orders necessary for the project to proceed during the first week of June.
"Once the decision is finalised, a letter setting out the full reasons for the decision will be published."
Building an M4 relief road - a scheme first proposed in 1991 - was a Labour election pledge by Mr Drakeford's predecessor, Carwyn Jones, and would be Wales' biggest infrastructure project since devolution in 1999.
Mr Jones had originally been due to be make the announcement on the new road before he stood down last December.
Conservationists say a new motorway across what they call "Wales' own Amazon rainforest" of the Gwent Levels would be a "direct attack on nature".
Meanwhile, an expert on government funding says tolls could help pay for the road.
In evidence to the assembly's finance committee, economist Gerry Holtham said the case for building the road through an agreement with the private sector "would be reinforced if it were a toll road -for which there are strong arguments".
He writes: "There is no obvious reason why tax payers in Anglesey should pay for commuters around Newport.
"And if the latter don't want to pay a toll they have the option of crawling along through the Brynglas tunnel."
Prof Holtham's suggestion follows the ending of tolls on the two M4 Severn bridges in December.
Welsh Government Rural Affairs Minister Lesley Griffiths declared a climate emergency on Monday, after protests demanding politicians take action on climate change, saying she hoped the declaration would trigger "a wave of action".
The SNP's Nicola Sturgeon made a similar declaration at her party's conference on Sunday and Labour is expected to press UK ministers to declare a national climate emergency on Wednesday.