JIAMUSI, China (AP) – The United States said Tuesday that it was sending experts to help China cope with a river-borne toxic spill that is approaching Russia’s Far East, while Beijing promised to work closely with Moscow to limit the damage.

The U.S. ambassador to China said the communist government had accepted the offer of an Environmental Protection Agency assessment team that would suggest ways to remedy effects of the 90-mile chemical slick.

Addressing business leaders in Hong Kong, Ambassador Clark T. Randt expressed concern that Beijing failed to react quickly enough to the benzene spill, which has disrupted water supplies to millions of people.

“It seems it took a while to come to the attention of the central government and of course, that’s a bit worrisome to us,” he said.

A Chinese Foreign Ministry spokesman said Tuesday that Premier Wen Jiabao had written a letter this week to his Russian counterpart that “reaffirmed China’s readiness to further cooperate with Russia to deal with the aftermath of the pollution.”

Benzene – a potentially cancer-causing compound – and other chemicals have been moving along the frigid Songhua River, which joins the Amur River in Russia. It is expected to reach Khabarovsk, a Russian border city of 580,000 people, early next week.

The slick has been stretching and slowing as the Songhua freezes and now is nearly double its previous, 50-mile length. Its concentration of toxic nitrobenzene was more than eight times the acceptable level, China’s official Xinhua News Agency said.

The spill reached Jiamusi in northeast China early Tuesday. The city of 480,000 people rushed a new water plant into operation as supplies from near the river were cut back drastically to prevent contamination.

The Chinese government did not confirm that benzene had polluted the Songhua until Nov. 23, 10 days after the spill and just before the chemical reached Harbin, a city of 3.8 million people.

In Hong Kong, Randt said slow official reaction worried the U.S. in part because, “We remember SARS and how that took a little while to come to people’s attention.”

China was similarly accused of hiding bad news during an outbreak of severe acute respiratory syndrome in 2002 and 2003.

Harbin was forced to shut down running water for five days, forcing residents to stand in sub-freezing weather to get water from tanker trucks brought in by the local government. Hotels, restaurants, factories and other businesses were badly hurt.

Chinese media have accused local Communist Party leaders of trying to conceal the spill.

Beijing already has apologized to Moscow for the toxic slick, which was caused by a chemical plant explosion that killed five people and fouled the river with 100 tons of chemicals, including vast amounts of benzene, which is used in making plastic, detergents and other products.

The director of China’s environmental protection agency has resigned and the general manager of the chemical company blamed for the spill was removed from his post. But there has been no sign Communist Party officials might be punished.

In the first details of the disaster’s expected economic impact, a report by the state-run Web site Northeast Net said the government of Harbin is borrowing $79 million to pay for recovery efforts.

The government hasn’t said whether businesses, farmers, fishermen and others affected by the disaster would receive compensation.

On Friday, Jiamusi shut down three of the seven wells that feed its main water plant, saying they were close to the river and could become contaminated.

A new water plant was rushed into operation because of the spill, and the government at one point had 1,500 people working around the clock to complete construction, the local party newspaper Jiamusi Daily said.

“We’re ready. Control and prevention work has entered a critical stage,” Mayor Li Haitao told Xinhua.

“We’ll do whatever we can to ensure drinking water safety and maintain normal, stable social order in urban as well as rural areas,” he said.

The main water plant’s output has fallen from 34 million gallons daily to as little as 5 million gallons a day, said Wang Li, its deputy general manager.

Wang said the plant had supplied up to 80 percent of the city’s running water, serving some 600,000 people in Jiamusi and surrounding areas.

AP-ES-12-06-05 1639EST