INTERVIEW-Ferrovial to step up acquisition drive

* Eyes deals in U.S., Canada, Middle East and Australia

* To present letter of interest for Chicago's Midway

* To keep 34 percent stake in Heathrow Airport Holdings

(Adds details and background)

MADRID, Feb 22 (Reuters) - Spanish infrastructure company Ferrovial is on the hunt for more acquisitions as it seeks to diversify further from its crisis-hit domestic construction business.

The owner of Heathrow Airport Holdings - formerly BAA - is ending a five-year drive to reduce debt through asset sales and has more than 1 billion euros ($1.3 billion) of cash to spend, even after Thursday's 385 million pound ($587 million)acquisition of British maintenance and utility company Enterprise.

Ferrovial ran into debt trouble after scooping up BAA in 2006, but has since sold stakes in the company at a profit.

"We've strengthened our balance sheet and now have a healthy financial situation, that allows us to look for investment opportunities while rotating (selling) mature assets," Chief Exceutive Inigo Meiras told Reuters on Friday.

Now the company is eyeing infrastructure opportunities in the United States, Canada, Colombia, Australia and the Middle East, he said, and will present a letter of interest for the privatisation of Chicago's Midway airport.

Ferrovial has sprung from a small family-owned railroad construction business founded in 1952 to one of the world's largest infrastructure companies, with airport, toll road, construction and services assets in more than 15 countries.

With its construction arm in Spain suffering from a sharp economic downturn and virtual halt in public tenders, the company has relied increasingly on its overseas business, with Europe's biggest airport Heathrow and Canada's 407 ETR toll road its main growth drivers.

The company, with a price-to-earnings ratio (PE) of 6.85 compared with an average 23.7 for the European infrastructure sector, posted revenues of 7.7 billion euros in 2012.

Ferrovial is "comfortable" with its current 34 percent stake in Heathrow Airport Holdings, held through FGP Topco, after selling down its stake from more than 50 percent in the past 18 months to remove debt from its balance sheet and generate cash.

According to a recent shareholders pact, Ferrovial can reduce its stake in Heathrow to 25 percent and analysts have tipped the possibility of more sales, given the above-expected valuation fetched in previous sales.

Ferrovial shares, which gained 20 percent last year, were trading flat at 11.91 euros per share on Friday, against a 1.4 percent gain on Spain's blue-chip index. ($1 = 0.7563 euros) ($1 = 0.6555 British pounds)

(Editing by Fiona Ortiz and David Goodman)