Salvage workers struggled to begin pumping oil from a stricken container ship off the New Zealand coast as approaching foul weather threatened to disrupt the recovery. Meanwhile, authorities began to reopen sections of popular beaches near where the cargo vessel Rena ran aground 11 days ago after a volunteer army removed more than 600 tonnes of oiled sandy waste. The government is seeking a meeting with the shipping firm that chartered the Rena, saying it was not happy with their response to New Zealand's worst maritime pollution disaster. Transport Minister Steven Joyce said he had called for talks on Monday with the Mediterranean Shipping Company, the world's second largest container shipping firm, saying "they have to step up and be part of this exercise". The Rena remained teetering on the reef, but in calm waters, and Maritime New Zealand (MNZ) on-scene commander Nick Quinn said it was hoped to begin pumping oil to a nearby tanker on Sunday. "The speed of the operation will depend on a range of factors including weather, the stability of the vessel and the viscosity of the oil. This will be a long process," he said. Salvage personnel have said that their main difficulty without power from the ship's engines was heating the fuel, which has cooled to a dense consistency, making it harder to pump. Although the forecast was good in the immediate future, rising seas were forecast for Monday night. It is believed 1,346 tonnes of oil remain on board the vessel, which was carrying 1,673 tonnes when it ploughed into the Astrolabe Reef early on October 5. The spilled oil has killed about 1,000 birds and has been washed up on once pristine beaches, bringing thousands of volunteers to the seashore to mount a clean up campaign. The mass effort to clear away hundreds of tonnes of sludge allowed authorities to reopen public access to a small section of beach on Sunday, although Quinn warned that changing tides and weather conditions could bring more oil ashore. "People shouldn’t panic if they do see some oil around there. It’s been three days since we got any fresh oil off the ship and so the oil that is out there is weathered and less toxic than any fresh oil," he said. "We are here for the duration of this response. When oil turns up on the shore, we will get it clean and open to the public as soon as we can. And if we need to, we will do that again and again." The Rena was off course when it ran aground and the New Zealand government has accused the captain of attempting to take a short cut on his way to the port of Tauranga on the east coast of New Zealand's North Island. The captain and the officer on navigational watch when the Liberian-flagged ship ran aground have been charged with operating a vessel in a manner causing unnecessary danger or risk. The charge carries a maximum penalty of one year in jail. While the salvage operation continued, the New Zealand navy was patrolling the area locating containers which had fallen from the teetering vessel and posed a hazard in the shipping channel.