The Google case has given the US an opportunity to re-adopt its hard-line approach, and move away from the "smart" diplomacy it had used against China of late, experts tracking the issue said on Thursday.

Calling the affair "politicized", the experts also suggested that the government take steps to ensure that a monopoly situation does not prevail in the search engine market. They were referring to the perceived gains Baidu, Google's arch rival in China, would make in case the US search giant pulled out of the country.

Professor Jin Canrong, a leading US studies expert at the Renmin University of China, said Washington was adopting a tougher approach, as the "smart diplomacy", coined by Secretary of State Hillary Clinton, had not worked very well.

"Now, she is focusing more on issues like human rights and press freedom. The Google case is part of that," Jin said.

In January, the US-based search engine giant threatened to stop censoring its results on Google.cn and pull out of the country. The company alleged that it had suffered from a series of cyber attacks supported by the Chinese government, without showing evidence to back up its claim.

Though Chinese officials have repeatedly expressed hope that Google would not shut shop, a recent report in the Financial Times said the company was "99.9 percent certain" to close Google.cn.

Google's top management was "adamant" about ending the censorship, the London-based newspaper quoted an unidentified source "close to the search company" as saying.

Amid the impasse, Chinese firms selling advertising space on Google's search pages have demanded clarity about the search giant's plans in China.

A letter purportedly from 27 Google-authorized sales companies showed on Wednesday the wait had gone on for too long, eroding their business, scaring off employees and putting big investments in jeopardy.

"We see a constant stream of information but cannot predict the future, we see business sliding, but there is nothing we can do," according to the letter. "We are waiting now in incomparable pain and disquiet."

Google has received the letter and is reviewing it, spokeswoman Jill Hazelbaker said.

If Google did leave, "the impact on the Chinese market will actually be limited", Jin said, adding others may fill up the space.

Tencent, best known for its flagship product, an instant-messaging program with hundreds of millions of users, is already developing its own search engine, the Wall Street Journal reported recently.

"The government should oppose Baidu's monopoly if Google leaves," Jin added.

Yu Guoming, the vice-president of the Journalism School at Renmin University, however, said it would be a huge loss both for China and Google, if the company did leave.

China had a lot to review over the Google case, Yu said. "China's Internet censorship system is not transparent enough," he said.

He said strict censorship is reasonable according to China's own special characteristics. "But, the key is that the law enforcement needs to be transparent. Many contents are censored not for national security reasons, but to protect some interest groups."

Yu said it would be hard for Google to give up the Chinese market with roughly 400 million Internet users. "It will come back one day even if it leaves now."