aBRITISH Telecommunications and American company AT&T are likely to have to wait a further four months before learning if their global joint venture can go ahead.

A senior European Commission official admitted in Brussels yesterday that it was ''very likely'' an extensive inquiry into the proposed #6bn link up of the companies' international telephone operations would take place when it completed its initial four-week examination, early next month.

The decision by the commission to use its merger rules - which allow it to extend its original investigation by four months if it has ''serious'' concerns that a merger will have an excessive share of EU markets - is not unexpected.

''No big telecoms venture is ever likely to go through after just a four-week investigation,'' explained one Brussels source.

Under its competition rules, the commission can block mergers and ventures between companies with combined global sales of 5bn Ecus (#3.6bn) and EU sales of 250m Ecus each, if it believes that these would strengthen a dominant position in European markets, even if the companies are from outside the union.

The commission, which can insist that certain conditions are complied with before mergers may go ahead, is understood to be looking particularly closely at the two companies' combined 20% share of cables which carry calls between Europe and the US.

Although the joint capacity may be higher than the commission would be comfortable with, the fact that other competitors are entering the transatlantic market is likely to ensure that there is sufficient competition for the merger to go ahead.

While both companies may now have to wait until April for the commission's verdict, analysts predicted last night that Brussels was likely eventually to approve it, although it must also be cleared

by the US Department of Justice and the Federal Communications Commission.