The United States has called off plans to send food aid to North Korea, after the impoverished state launched a rocket in defiance of international demands.
A UN agency says that more than three million people in the country could go hungry this year as a result of insufficient food supplies.
The United States had already suspended the plan to deliver 240,000 metric tonnes of assistance aimed at children and pregnant women as North Korea prepared what the government called an unsuccessful bid to put a satellite in orbit.
'Impossible' to move forward
The US government, which had been fine-tuning the aid package for months before finally announcing it on February 29, said that it would be "impossible" to move forward with it after the rocket launch. The US considers the launch to have been a veiled missile test.
Barack Obama, the US president, said that he was deeply concerned by the rocket launch, which violated UN Security Council resolutions, although he noted that "they've been trying to launch missiles like this for over a decade now and they don't seem to be real good at it".
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"We will continue to keep the pressure on them and they'll continue to isolate themselves until they take a different path," Obama said in an interview with Telemundo.
Ben Rhodes, Obama's deputy national security advisor, said that the US would not be going forward with agreements to provide "any assistance" to North Korea, because the country's government "could not be trusted to keep their commitments".
He said that additional sanctions could be put into place following the launch.
Under the February 29 deal, the US was to deliver aid, under supervision, to North Korea, with the latter obligated to freeze nuclear and missile tests in return.
Asked if the food aid cut-off was permanent, Mark Toner, the US state department's spokesperson, said that the US could no longer "frankly trust the North Koreans that this will end up in appropriate hands".
Hillary Clinton, the US secretary of state, spoke about the rocket launch on Friday with China's foreign minister, Yang Jiechi.
"We're asking them to use their relationship with North Korea to convey our concern about their recent actions," Toner said.
Hundreds of thousands of North Koreans are believed to have died in a famine in the 1990s. UN agencies estimated in November after a visit to the North that three million people would need food aid in 2012.
Mercy Corps, one of five US non-governmental groups that would have delivered the aid, said that the assistance would have reached more than two million North Korean children, as well as tens of thousands of pregnant women.
David Austin, the North Korea programme director for Mercy Corps, said that the United States for generations had donated food to the needy regardless of political considerations.
"It is a shift to using food as a policy tool and it's one that we have a lot of concern about. We think it's become a distraction because it removes the focus from people who are in need and people whom we can save," he told AFP.
Austin, who visited North Korea in March, said that an administrator at an orphanage had told him that the children at his facility were receiving 60 per cent of their normal rations, and had not eaten any protein in two months.
The European Union last year announced $13 million in aid to provide food for North Koreans.