Carillion said the value of its order book plus probable orders at the half-year stage was about £17.4bn, matching last year's.
It still expects first-half performance to be led by revenue and margin growth in support services.
This part of its business is moving towards making up two thirds of the group's total underlying operating profit.
The group expected its total first-half revenue to increase and offset the effect on first-half profit of a slight reduction in underlying operating margin.
It blamed this on the amount of equity sales in public-private partnership (PPP) projects being lower than in the first half of 2015 and the one-off contribution to profit from the reorganisation of Middle East labour facilities in the first half of 2015 was not repeated in 2016.
Revenue predictability for 2016 had increased to about 97% from 84% at the end of last year.
Carillion said its line-up of specific contract opportunities was worth about £41.5bn against £41.4bn a year earlier.
The group said it was too early to predict the impact of the EU referendum vote in the UK but noted it had little business in mainland Europe and it had put in place robust contingency plans.
"We continue to expect our full-year performance to be led by revenue and margin growth in support services, with PPP projects, Middle East construction services and construction services excluding the Middle East also performing in line with expectations.
"The group remains on track to make further progress in 2016."