The Welsh Assembly claims talks with Richard Rogers Partnership are 'on the verge of success' and that the practice will be 'officially back on' the Assembly building project by next month.
The move will allow the Assembly to release Welsh practice Stride Treglown, which it had retained in case negotiations broke down.
RRP was controversially sacked from the scheme in 2001 by Welsh finance minister Edwina Hart after a bust-up over fees.
However, the practice was reappointed in February under the proviso that contract terms would be successfully renegotiated by mid-July.
An assembly spokesman told the AJ: 'We believe the talks have been very positive. At the moment it seems very unlikely that we will have to call in the Stride Treglown back-up.'
RRP declined to comment.