Terra Industries, the US fertilizer maker under offer from rival CF Industries, has sidestepped a showdown with its potential acquirer by a last-minute change to the smallprint of its company rules.

Terra has exploited a recent change in Maryland corporate law to scrap a deadline of May 15 when it could hold this year's annual meeting, a stock market filing shows.

While the company had been obliged to hold the meeting within a 31-day period, it will now be hold it whenever it likes within a calendar year.

The change appears to dash CF Industries' plans to use an imminent Terra annual meeting to force a change of management at its target. CF Industries has nominated its own candidates as replacements for three Terra directors due for re-election this year.

And it comes just as Stephen Wilson, the CF Industries chairman and chief executive, was attempting to step up the heat.

'Appreciate an explanation'

In a letter to Terra chief executive Michael Bennett on Tuesday, Mr Wilson said he would "appreciate an explanation as to why [Terra] have not yet announced your meeting arrangements".

And he questioned a request from Terra, which has refused to engage in takeover talks, for a list of CF Industries investors.

"We want to give you the opportunity to explain to the Terra stockholders, and to us, why you appear to be more interested in communicating with our stockholders than in negotiating a merger agreement with us," Mr Wilson said.

'Significant factor'

CF Industries is fighting its own hostile takeover approach, from Canadian rival Agrium.

Terra said a delay to its annual meeting would give shareholders "the benefit of all relevant information" at the time of the session.

"The status of Agrium's offer for CF will be a significant factor to be considered by the [Terra] stockholders at [Terra's] annual meeting, which has not yet been scheduled," the filing said.