Breach of the covenants has been caused by a pounds 7.2m write- down of values on its 80 pubs, 77 of which were owned by the old Wiltshire Brewery.
The conditions of the covenants were built around unspecified loan-to-value ratios.
United's main bankers are Allied Irish Banks, which sold 37 pubs to Wiltshire Brewery in 1992, Yorkshire Bank and National Home Loans.
The write-down has eliminated distributable reserves. It is believed that shareholders' funds are below pounds 2m, and debts are about pounds 8.5m.
Michael Roberts, finance director, and David Ford, property director, have resigned. United said Mr Roberts had left to pursue other interests, but would still work full-time to assist the refinancing.
United, chaired by Vija Mallya, who also runs UB, the biggest drinks company in India, said Mr Ford would receive no compensation. He earned pounds 32,000 a year and was on a three-month contract.
It said the matter of compensation for Mr Roberts, who was on a one-year contract worth around pounds 40,000 a year, had not arisen because he was still employed by United.
Stephen Lambert, a chartered accountant, has been recruited as finance director. He held the same post at Holmesquest Holdings, a private company which makes communication equipment.
United intends to present shareholders with proposals for a big financial restructuring and for acquisitions, which it said were essential to improve critical mass.
Industry sources say the acquisitions are two drinks companies, one of which is UBSN, the 50 per cent-owned joint venture with Shepherd Neame, the Kent brewery.
UBSN mainly distributes Kingfisher, the lager sold in every other curry house in Britain.
United said the acquisitions were likely to be combined with an equity issue. 'It is anticipated it will take two months before details are published,' it added.
UB of India, holder of 15 per cent, is providing interim funds until the refinancing, which should be accompanied by results for the year to last November. In August United reported that losses narrowed from pounds 284,000 to pounds 189,000.
United shares fell from 7p to 4.5p on the news.