E.C.B. Government Bond-Buying Program Grinds to a Halt FRANKFURT - The European Central Bank said Monday that it had made no purchases of government bonds last week as it put on hold a controversial program aimed at lowering borrowing costs for indebted countries. Its purchases had already dwindled to a negligible €59 million, or $78 million, the week before that. The bank has been buying bonds from other investors in the secondary market in an effort to push down borrowing costs, particularly for Italy and Spain, which have come under pressure amid the debt crisis in the euro zone. But the central bank has reined in its purchases as a new program of large-scale cheap credit for banks has helped reduce strains in the financial system. The bond purchase program was introduced in May 2010 in a largely unsuccessful attempt to reduce borrowing costs for Greece. It was later put on hold, from March 2011 until August that year, when the euro zone crisis worsened and borrowing costs rose for indebted countries as fears of default surfaced. Thereafter, the E.C.B. used the bond-buying program as a tool to lower borrowing costs that threatened to drive Italy and Spain into default. The central bank has since eased off its purchases after deploying a larger-scale program to offer inexpensive, long-term credit to banks. Some of those banks in turn used the money to buy higher-yielding government bonds, facilitating governments" access to affordable credit without violating a legal ban that prevents the central bank from financing governments. A first infusion of €489 billion that was taken by 523 banks has led to lower borrowing costs; a second round is slated for Feb. 29. The bond purchases were criticized in some quarters as an inappropriate bailout effort by the E.C.B. Because of the purchases, the E.C.B. has also had to take measures to avoid incurring losses on its Greek bonds while the government in Athens negotiates a debt reduction deal with its creditors. The central bank is swapping its Greek bonds for new ones that are not supposed to be subject to the reduction.