This time around, tensions already are surfacing over what model the combined exchanges would employ to process and settle trades.

Euronext processes and settles trades through companies it does not control, LCH.

Currently, there is no central platform to clear and settle locally denominated trades in Latin American debt.

The firms are required to "settle" trades - make sure a seller's records and a buyer's records are in accord - within five days.

The system will initially shorten the time it takes to settle trades in Britain to three days from five days.

They must settle trades over a few days or months, rather than years.

Many volunteered to work double shifts to clear and settle trades.

Different laws, customs, languages and clearing mechanisms create many difficulties in settling international trades.

Second, it will settle individual trades in "real-time", rather than grouping them all together and netting the outcomes between the various participants.

Other markets long ago developed clearinghouses to settle trades and manage the resulting open positions in derivative contracts.