The EU's top economic official, Pierre Moscovici, said the bloc understood that Britain should not be rushed but "at the same time ... let's not waste time, let's not have too much uncertainty, let's act and choose as swiftly as possible."
Hammond told reporters on Sunday the two-year negotiating period, once launched, represented "quite a tight timescale" and Britain needed to go into it with clear objectives.
"We have to do that before the start of the process because when we serve that notice, we need to hit the ground running," he said.
But Hammond also showed he was aware of the need for some clarity on Brexit: "What will start to reduce uncertainty is when we are able to set out more clearly the kind of arrangement we envisage going forward with the European Union."
"If our European Union partners respond to such a vision positively - obviously it will be subject to negotiation - so that there is a sense perhaps later this year that we are all on the same page in terms of where we expect to be going, I think that will send a reassuring signal to the business community and to markets," Hammond said.
May has said she does not plan to launch the formal negotiation period this year. It remains to be seen if other EU countries would enter informal talks with Britain before the formal negotiations, something they have previously ruled out.
Financial markets have stabilised after the initial shock of the referendum result which saw the value of the pound plunge by more than 10 per cent and trillions of dollars wiped off stock markets worldwide. But economists are expecting Britain to fall into a recession, according to a Reuters poll.
Hammond said he did not think that a survey of British businesses published on Friday, which showed the sharpest fall on record in a purchasing managers index, was a sign that the economy was in already in a recession.
"What it does is underscore the hit to confidence," he said.
- Reuters