The cash call is part of a 2 billion euro capital strengthening plan, which also includes asset sales and the refinancing of existing debt, aimed at cutting Astaldi's debt burden.

Under a new business plan unveiled on Wednesday, Astaldi plans to lower its debt 1.6-1.7 billion euros this year from 2.3 billion euros in 2017 and reduce it further under 1 billion euros in 2022.

Astaldi and IHI have built together Turkey's Osman Gazi bridge, the world's fourth longest suspension bridge, and in January won a contract to build a suspension bridge over the Danube in Romania.

"Through the strategic partnership, Astaldi and IHI will consolidate their integrated capacity for construction of large-scale infrastructure projects," Astaldi said in a statement.

The group's controlling shareholder FINAST will continue to hold 50.2 percent of the company's voting rights after the cash call and the deal with IHI.

Astaldi reported a 7 percent drop in first quarter revenues to 604.1 million euros, hurt by one-offs and foreign exchange effects.

The group targets revenues of more than 3.5 billion euros next year under the plan, compared with 3.1 billion euros last year.

Earnings before interest tax depreciation and amortisation (EBITDA) fell to 75 million euros in January-March, from 85 million euros a year earlier.

Astaldi targets an EBITDA of more than 350 million euros this year and the next, from 367 million euros last year.

Astaldi said banks with whom the group has close ties were open to joining an underwriting consortium JPMorgan Securities will be looking to put together as the cash call's sole global coordinator.

(Reporting by Stefano Rebaudo, editing by Valentina Za and Louise Heavens)