Anger over Washington's extensive eavesdropping on world leaders and ordinary citizens has shown no signs of abating, as observers say using anti-terrorism as an excuse for pervasive surveillance is "hypocritical and abused".

Chinese experts said the disclosure shows the United States is making the most of its intelligence capabilities to secure its supremacy in the world, and the scandal will weaken its global credibility.

Observers also said the scandal may prompt new international rules to rein in transnational spying as 21 countries have reportedly asked for a UN draft resolution against the US surveillance.

The latest reports reveal the US was responsible for broad surveillance of the communications of as many as 35 world leaders and likely millions of foreign nationals.

The leaders monitored through the National Security Agency phone tapping included German Chancellor Angela Merkel, who was reported to have been spied on by the US since 2002.

The NSA was also accused of accessing tens of thousands of French phone records as well as tracking 60.5 million telephone calls in Spain in a single month.

Qu Xing, president of the China Institute of International Studies, said Washington has been highly concerned by European integration, as Europe would surpass the US to become a new power center if the EU worked as successfully as expected.

But Qu said US-EU relations will forge ahead in the long term despite the recent setback.

"The US and Europe are like a pair of business partners. Both benefit from a cooperative relationship and neither can put up with the consequences of a breakup," Qu said.

Shi Yinhong, a senior expert on US studies at Renmin University of China, said, "Perceiving itself as a superpower, the US holds the arrogant attitude that it is not a big deal to steal other countries' information".

In another development, Japanese media revealed over the weekend that the NSA approached the Japanese government in 2011 to allow it to tap the international fiber-optic cables that traverse the country and carry much of the traffic across East Asia, in an attempt to gather more information on China.

Calling cybersecurity "a matter of sovereignty", Foreign Ministry spokeswoman Hua Chunying urged the international community on Tuesday to set up a new security concept of mutual trust, benefit and equality, and to create binding regulations within the UN framework.

"China and Russia have submitted a draft plan, in an effort to help the world jointly tackle the problem," Hua said.

Experts said Washington not only offends its allies by the extensive monitoring, but also harms mutual trust.

Dong Manyuan, deputy director of the China Institute of International Studies, said Washington can hardly find any excuse for its wiretapping.

"Originally, the US claimed that it monitored billions of calls worldwide to fight terrorism. However, the reality shows that Washington has expanded its monitoring to Merkel and other European leaders, who share the same values as (US President Barack) Obama," Dong said.

Washington recently denied that Obama was informed of the operation against Merkel in 2010.

"Obama did not halt the operation but rather let it continue," German newspaper Bild am Sonntag quoted a high-ranking NSA official as saying. A poll by a German magazine found that 60 percent of Germans believe the scandal has damaged ties.

The White House on Monday acknowledged that more constraints are needed regarding the NSA's surveillance practices to ensure that privacy rights are protected.

"We need to make sure that we're collecting intelligence in a way that advances our security needs and that we don't just do it because we can," White House spokesman Jay Carney said.

The spying row prompted European leaders last week to demand a new deal with Washington on intelligence gathering that would maintain an essential alliance while keeping the fight against terrorism on track.

Swiss President Ueli Maurer warned the revelations risked "undermining confidence between states".

"We don't know if we're only seeing the tip of the iceberg or if other governments are acting in the same ruthless manner," he told reporters.

Analysts said the exposure of the US surveillance and the subsequent global anger may lead to the birth of a binding international agreement on spying through telecommunications and cyberspace.

Shi said the series of eavesdropping operations may accelerate the formulation of rules in the global community, but it will be extremely difficult.

"In fact, international rules can only help in a limited way. What we can do is protect ourselves technically," Shi said.

During the weekend, Germany and Brazil drafted a UN General Assembly resolution that condemns "indiscriminate" and "extra-territorial" surveillance, and ensures "independent oversight" of electronic monitoring.

The draft has enlisted 19 other countries including US allies Mexico and France.

Brazilian President Dilma Rousseff canceled a trip to the US last month over allegations the NSA intercepted her office's communications.

Guo Xiangang, vice-president of the China Institute of International Studies, said Washington will restrain its "current unbridled behavior" if a UN resolution comes into force, but it will never give up surveillance of other countries, including its allies.

"Despite a rift with allies, the US will further integrate its intelligence power to continue actions that fit its national interest," Guo said.