Britain will make available 20 billion pounds ($31 billion) for a guarantee scheme to back loans to small and medium sized companies to cut their borrowing costs and help boost the economy, Chancellor George Osborne said on Sunday.

We are making available 20 billion pounds for the National Loan Guarantee Scheme, however it sits within an envelope that could be as large as 40 billion pounds, he told BBC television.

He said he had signed a deal with pension funds to invest in infrastructure projects and was confident of meeting the government's debt reduction and fiscal targets.

Osborne was speaking ahead of his autumn budget statement next week when he will detail plans to revive a stagnant economy and avoid a double-dip recession in a growth package hamstrung by the euro zone debt crisis and a strict austerity drive.

($1 = 0.6458 British pounds)

(Reporting by Tim Castle; Editing by Tim Castle)