ABOARD XUELONG, Jan. 6 -- Trapped Chinese research vessel and icebreaker Xuelong warmed up its engine and tried to broaden an "ice-breaking runway" on Monday, preparing for a possible westerly wind favorable for its breaking-out.

However, interrupted by an unfavorable southeast wind and a decreasing tide, the broadening only lasted for forty or fifty meters, a Xinhua correspondent aboard the vessel reported.

The icebreaker became trapped in thick sea ice on Friday, just a day after its helicopter Xueying evacuated all 52 passengers from the stranded Russian ship Akademik Shokalskiy to the Australian icebreaker Aurora Australis.

Weather reports forecast that the prevailing southeast wind will gradually turn into a northerly wind throughout Monday and become a class 3 or 4 westerly wind on Monday night.

Though a little weak, the westerly wind is expected to provide favorable weather conditions for Xuelong's breaking-out. The icebreaker will warm up again on Monday afternoon to prepare for the potential window of opportunity.

But there are three major uncertainties within the window.

First, it is uncertain whether the westerly wind will be strong enough to push away the drifting floes currently surrounding the ship, especially on its starboard. The floes there are three or four meters thick -- three times thicker than the vessel's maximum ice-breaking capability.

Second, no one can be certain how the wind will influence the iceberg in front of the ship, which is sometimes as close as 1.2 nautical miles (about 2.22 km) to Xuelong.

Third, it is hard to tell how the high-pressure weather system brought by the westerly wind will affect the sea area in which the icebreaker has been trapped.

In order to ensure that the vessel does not become fully frozen into the ice, the iceboat created a kilometer-long "ice-breaking runway" by sailing back and forth, while waiting for favorable weather conditions to break the siege.

Wang Jianzhong, captain of Xuelong, said that Xuelong has been surrounded by swiftly-amassed floes due to lasting strong winds in the past days, with the thickest ice layer reaching 3 meters to 4 meters. The area in which the ship is trapped has rapidly drifting icebergs and floes, and is some 21 km away from the nearest ice-free waters.

It is difficult for Xuelong to break the ice in such an area with one iceberg ahead and another moving closer slowly from behind, Wang said.

Xuelong could get out of trouble as long as it can break through the thickest floe zone some 2 nautical miles (about 3.7 km) long, Wang said, but it is important for the icebreaker to find an opportunity. The vessel currently has food supplies to last until April and fresh water supplies for a month.

Russian ship Akademik Shokalskiy became trapped on Christmas Eve, and Xuelong's onboard helicopter rescued the stranded passengers on Thursday, before its own movement was blocked by a one-km-long iceberg drifting northwest.