Freddie Mac and Fannie Mae, the US mortgage refinancing agencies and the two biggest single issuers of non-government bonds, could be the biggest beneficiaries of the US Treasury's decision to abandon sales of 30-year bonds.

Long-dated bonds issued by Fannie Mae and Freddie Mac, which are rated triple-A and used as proxies for government debt by bond investors, saw an upsurge in demand in the secondary market after Peter Fisher, the US Treasury under-secretary for domestic finance, announced the decision on Wednesday. Debt market traders said that institutional investors had reacted by buying up agency debt as well as existing 30-year Treasury bonds.