In M&A, there has never been a more apt time for Patrick Bateman's slip of the tongue in American Psycho. The character says he works in Murders & Executions.

For the first time in five years, more deals are being killed than being unveiled as companies cite financing uncertainties and the economic downturn as the main reasons for walking away.

In less than a week, the roll call of dead mergers has notched up companies in Europe, the US and Asia.

These include EDF's abandoned plans to make a new €4bn ($5.3bn) offer for Constellation of the US; Waste Management withdrew its $6.73bn offer for Republic Services; and PCCW halted the sale of a stake in its new HKT unit.

"A lot of transactions are falling over not because of the lack of financing per se, but because of the difficulties of refinancing in a short time scale, for example through bond issues or disposals," said Tom Cooper, vice-chairman of investment banking at UBS .

Short-term refinancing rates have become increasingly expensive in recent weeks, causing companies to be much more cautious about the risk of M&A in the short to medium-term.

This was one of Xstrata's reasons for walking away from an indicative £33-a-share bid for Lonmin earlier this month.

Although Xstrata had commitments from banks for a $15bn loan to cover the acquisition, a large portion of this debt was offered as one-year facilities, leaving Xstrata exposed to refinancing risks.

However, not all these deals will be left in the deep freeze. Bankers expect some bidders to revisit their acquisition plans once financing costs ease and investor confidence is restored.

Bidders such as Xstrata have left the door open by buying large blocking stakes in their target companies.

The Anglo-Swiss miner now holds almost 25 per cent of Lonmin, which prevents other bidders from gaining control.

"M&A is about careful timing. At the moment, chief executives are reluctant to bid until they can see some consistency, and less volatility, in the markets," said Henrik Aslaksen, co-head of global M&A at Deutsche Bank.

"If the performance of a target company is going to deteriorate and multiples collapse, then CEOs will wait to buy the same target later for a better price."

It is a shrewd tactic, but it does not always ensure the bidder will return. An example is Vinci's abandonment of its £517m offer for TBI, the UK airport operator, in the wake of the September 11 2001 terrorist attacks.

Vinci had a 14.9 per cent stake in TBI, but when markets stabilised it never returned with another bid because it had changed its outlook on the attractiveness of airport assets.

Choosing to abandon a deal in the current economic climate can also be advantageous for the bidder.

JCDecaux was rewarded by investors when it ended talks to acquire News Corp's eastern European billboard business this week, because of difficult market conditions. Shares in the French outdoor advertising group shot up 14 per cent on the announcement.

For News Corp, however, the loss of the sale means the loss of cash it needed to fund its expansion of pay-television interests in western Europe.

General Motors also found itself without a source of much-needed cash last month after Navistar International, the world's fourth-largest truckmaker, walked away from its planned acquisition of GM's medium-duty truck unit.

Conserving cash now may be a smart move for these companies as they reduce their cost bases while trying to protect shareholder value.

The deals that have been abandoned so far have yet to trigger any heated arguments between buyers and sellers.

This is in sharp contrast to the deals that were pulled in 2001 after the collapse of telecoms, media and technology stocks, when companies behaved more aggressively in testing the value and limitations of material adverse change clauses.

These allow a buyer or seller to walk away from a deal in the event of a material adverse change in the business, operations or financial conditions of a company.

Yet invoking such clauses is notoriously difficult, as Sir Martin Sorrell, chief executive of WPP, the global media and advertising group, found out.

Just days after the September 11 attacks, Sir Martin tried to terminate his acquisition of rival advertiser Tempus, claiming a material change had occurred that would affect the target.

However, the Takeover Panel, the UK watchdog, ruled that WPP could not prove that such a momentous event would have a long-term effect on the industry.