Britain has given an extra £5 million food and education aid to Zimbabwe and promised more if the country can show it is on the road to real democratic reform.
Prime Minister Gordon Brown said there were "great signs of progress" in the wake of February's power-sharing deal between President Robert Mugabe and long-time foe Morgan Tsvangirai.
But following talks at 10 Downing Street with Mr Tsvangirai, now prime minister, he warned that the UK would continue to watch for and criticise signs of renewed repression.
Mr Tsvangirai has struggled to raise the large sums of financial help he wants from foreign governments which remain wary of giving cash directly to Mr Mugabe and his allies.
Mr Brown said the extra cash - which brings this year's transitional help from the UK to £60 million - would be delivered via aid agencies, not the Harare administration.
"We are prepared to respond when the Zimbabwean government takes action which is in conformity with the long-term ambition," the Prime Minister said.
"But we will continue to speak out for those who are intimidated and threatened and exploited and indeed against all censorship. We will continue to test the progress that is being made."
That includes a new constitution within 18 months, followed by elections, and an "immediate stop" to land seizures.
The new help will be made up of £4 million for "food security" and £1 million to provide text books for the newly-reopened schools, he said.
Mr Tsvangirai defended the power-sharing arrangement and insisted he was taking Zimbabwe on an "irreversible" journey of reform. The former opposition leader was heckled and booed at a meeting of Zimbabwean exiles living in the UK when he urged them to return, amid anger that he appeared to be legitimising the Mugabe regime despite continued criticism by bodies such as Amnesty International of human rights abuses.
