Zimbabwe, once a regional bread-basket, now relies heavily on aid
About half the population of Zimbabwe could soon be in need of constant food aid and medical assistance, the UN's humanitarian chief has told the BBC.
John Holmes said three million people were already reliant on aid, and that figure could rise to five million.
He said the situation was already grave and deteriorating.
However, he acknowledged that access for aid agencies had improved greatly since a political power-sharing deal was signed two weeks ago.
The opposition Movement for Democratic Change (MDC) and President Robert Mugabe's Zanu-PF agreed to work together after years of political and economic crises.
Under the deal, Mr Mugabe remains president while MDC leader Morgan Tsvangirai - who pulled out of a presidential election earlier this year, citing violence - will become prime minister.
On Monday, the president said he expected a unity government to be formed by the end of this week, but the MDC says talks have failed as Zanu-PF wants all the key ministries.
The hope is that a new government can overcome the acute economic crisis.
The planting season starts in five or six weeks
Zimbabwe's official inflation rate is still about 11 million per cent and there are severe food shortages.
Just ahead of the power-sharing agreement, the government lifted a ban on the distribution of food aid which had stopped aid agencies going to rural areas.
Critics had accused the ruling party of not distributing aid to opposition areas.
Mr Holmes warned that preparations needed to be made for next year's harvest to avoid millions more people becoming reliant on aid.
"Planting season for the next harvest starts in five or six weeks' time, at least for maize, and there is massive shortage of seeds and fertilisers in the country because of the economic situation," he told the BBC's World Today programme.
"We're looking to see whether we can accelerate even at this late stage and get some of those seeds and fertilisers and other imports into the hands of small farmers."
He said he hoped the farmers would plant more seeds "so they can harvest more, so we have less of a food assistance problem next year".