Sue Essex is due to address the Assembly

It is believed that Assembly Transport Minister Sue Essex will reveal that a decision on the project has been deferred.

The decision will in effect shelve the project for at least 10 years.

The idea of having a relief road for the congested M4 as it passes Newport is popular with civic and business leaders in south east Wales.

But the road has faced opposition from environmentalists and criticism over its cost.

Environmental objections have centred on the damage it could do to the Gwent levels, which is an important wetland wildlife habitat.

And the project would also be relatively expensive, costing an estimated �300m to �400m.

Dual carriageway

Elsewhere, Sue Essex is expected to approve plans to build a dual carriageway on the A40 between St Clears and Haverfordwest.

Work on the �60m project could start within five years.

In February, the UK Government announced that it is spending �22m on roads around Deeside in north Wales to cut congestion, delays and accidents.

The money will be spent on improving links between Deeside Industrial Park and the M56 over the border in England.