High altitude and unfavorable weather conditions in the quake-hit Yushu prefecture of northwest China's Qinghai Province had complicated rescue missions, officials said Saturday.

High altitude, low temperatures at night, and sandstorms had brought pressure and challenges to the transportation of quake relief supplies, rescuers and injured people, Vice Transport Minister Gao Hongfeng told a press conference.

Yushu sits at about 4,000 meters above sea level. Temperature in the region could drop below the freezing point at night at this time of the year.

Possible rainfalls and snow flurries forecasted in the region would also further complicate the situation, he said.

But the vice minister insisted that transport authorities had been experienced in and were capable of carrying out operations under such harsh circumstances.

"These issues might have brought difficulties to, but will not interrupt, our work," Gao said, adding that relief materials were currently being transported to the quake zones "nonstop."

"The shortage of relief supplies in the quake zones could be resolved in the near future," he said.

Xia Xinghua, deputy head of the Civil Aviation Administration of China (CAAC), also said high altitude of the Yushu airport had led to a limited access to the quake zones by air.

"The Yushu airport is located at about 4,000 meters above sea level," Xia said, "The CAAC has only 39 planes that can fly to the plateau, ... and we have ordered all these planes to be on standby for relief missions."