Concerns over water, food and other supply shortages are growing in Japan. But the government remains reluctant about throwing the doors open to all the world's disaster-relief agencies, many of which have held back on providing aid and volunteers out of a belief â ' increasingly being tested â ' that Japan can handle the disaster on its own.

Takeshi Matsunaga, a Japanese foreign-ministry spokesman, said in an interview Thursday that the government is 'not encouraging' volunteers to assist in tsunami-affected zones because the situation there remains unstable, with damaged transportation links and major strains on supplies.

Foreign aid often requires extensive logistical support to move equipment and to feed and house volunteers, and having more of them on the ground would put further demands on resources in areas where local authorities are already running low on supplies, he said.

'It's very difficult for the volunteers to go into the disaster areas, so at this point in time we are not encouraging volunteers to go into the area,' he said. 'It's purely because of the reality on the ground â ' it has nothing to do with unwillingness.'

He said the government does invite international support â ' it just prefers that it come in the form of donations arranged through its foreign missions overseas. 'We highly appreciate all the goodwill,' he said, adding it might be easier to accept more direct volunteerism once the disaster zones stabilize.

Some experts on humanitarian relief believe it may actually be better for Japan if not too many aid groups get involved. Many aid organizations in the past have come under criticism for failing to coordinate their activities and adding to confusion on the ground, and sometimes saddling countries with unwanted supplies such as winter coats for tropical climates.

Worries over the lack of food and other supplies have intensified over the past day or two amid reports that nearly half a million people are camped out in refugee centers in public buildings such as schools, with some people surviving on minimum rations, according to the International Federation of Red Cross. The United Nations said Wednesday that thousands of households remain without electricity and many survivors still lack protective clothing or blankets despite extraordinarily cold weather and snow, with emergency teams failing to reach some affected areas, leading to increasing frustration among residents.

Although international aid agencies have provided some support, including setting up children's centers to aid victims, many have held back on the kind of massive volunteer airlifts common when disasters strike poorer countries, such as Haiti or Indonesia, preferring instead to defer to Japanese authorities. Officials from the U.N. have said they have offered to provide any assistance necessary but can't force Japan to accept more volunteers or in-kind aid.

According to estimates by the U.N. Office for the Coordination of Humanitarian Affairs, by Wednesday Japan had received offers of aid from 113 countries, and accepted 14, mainly for search-and-rescue assistance.

Mr. Matsunaga asked for patience and understanding from the international community as Japan wrestled with the enormous logistical and other challenges it faces before inviting in more volunteers.

'It's better to look at the matter in phases because of the enormity of the destruction,' he said, adding that once the disaster zone stabilizes more opportunities to help could emerge.

日本民众对水、食品和其他物资短缺的担忧日益加剧。而政府仍不愿向世界所有救灾机构敞开大门。许多救灾机构已经暂停提供援助和派遣志愿者，因为相信日本可以自行应对这场灾难，然而这种信念正日益受到考验。 European Pressphoto Agency周三，搜救人员和搜救犬Rifka、Scanner从荷兰史基浦（Schiphol）机场出发前往日本。日本外交部发言人松永贵志（Takeshi Matsunaga）在周四的采访中说，政府“不鼓励”志愿者在海啸灾区提供帮助，是因为那里的局势仍不稳定，交通线路被毁坏，物资供应也严重短缺。 他说，外国援助通常需要大量后勤支持，用于运输设备以及为志愿者提供食宿，受灾地区政府已经面临物资供应日益不足的状况，志愿者增多会导致对当地资源的需求进一步增加。 他说，志愿者进入灾区十分困难，因此在这个时候，我们不鼓励志愿者进入灾区；这仅仅是出于对救灾现场的实际状况的考虑，与愿不愿意没关系。 他说政府确实在请求国际援助，只是更希望援助以日本驻外使馆安排的捐款的形式进行。他说，我们非常感谢所有人的善意；等灾区稳定后，接受更为直接的志愿服务会更容易。 一些人道主义救援专家认为，没有太多救援组织参与救灾实际上可能对日本更好。过去，许多救援组织受到批评，原因是它们未能协调好其救援行动、给救灾现场添乱，有时还为受灾国家提供不必要的物资，从而加重了这些国家的负担，比如给热带国家提供冬衣等。 据国际红十字会（International Federation of Red Cross）消息，过去一两天对食品和其他物资短缺的担忧已经加剧，有报道称近50万人在学校等公共建筑的避难中心外面露宿，其中有些人依靠最低定量维生。联合国周三说，数千户家庭依然断电，在极端寒冷的天气和大雪中，很多幸存者仍缺少防寒衣物或毯子。应急小组一直无法到达所有受灾地区，导致居民情绪日益不满。 尽管国际救援机构已经提供了一些支持，包括设立儿童中心帮助灾民。在海地或印度尼西亚等较贫困国家发生灾难时，国际救援机构往往会大规模空运志愿者进行援助，而这次许多机构并没有这样做，选择了遵从日本当局的建议。联合国官员说，他们已经提供了必要的援助，但无法强迫日本接受更多的志愿者或物资援助。 据联合国人道事务协调局（U.N. Office for the Coordination of Humanitarian Affairs）估计，截至周三，有113个国家主动提出要援助日本，其中14个国家的援助请求为日本所接受，主要涉及搜救工作。 松永贵志说，在邀请更多志愿者进入之前，日本正努力解决庞大的后勤问题及其他问题，他呼吁国际社会耐心等待并予以理解。 他说，鉴于灾区破坏的严重性，最好是分阶段看待此事，他还说一旦灾区稳定下来，会有更多提供援助的机会。