WASHINGTON (AP) — U.S. and Chinese officials began formal discussions on cybersecurity Monday, kicking off four days of talks to build cooperation and broach issues that divide the two world powers.

Washington is increasingly concerned about the Chinese theft of American intellectual property, but has been put on the defensive by the revelations about U.S. surveillance by NSA leaker Edward Snowden.

A bilateral working group on cyber issues that was announced in April held its first meeting Monday at the State Department, with both civilians and military taking part. The U.S. side was led by coordinator for cyber issues, Christopher Painter; China's by senior Foreign Ministry official, Dai Bing.

It's a prelude to annual, ministerial-level talks on security and the economy that start Wednesday, a month after a path-finding summit in California between President Barack Obama and new Chinese leader Xi Jinping that aimed to improve collaboration between the powers whose strategic rivalry belies deep economic inter-dependence.

This year's edition of the dialogue at least begins in less fraught circumstances than last year's in Beijing, which was overshadowed by the escape of dissident lawyer Chen Guangcheng from house arrest to the U.S. Embassy in the Chinese capital. Chen later moved to the U.S. where he's proved a staunch critic of Beijing.

But the weeks since Obama-Xi summit have brought a new complication in the relationship. Authorities in the semi-autonomous Chinese territory of Hong Kong refused to extradite Snowden — a move which U.S. officials implied that Beijing had a hand in.

Officials are likely to play down those differences in this week's talks, but cybersecurity is front and center. The Obama administration says resolving it is key to the future of ties between the world's two largest economies, and U.S. businesses are also speaking out.

"The U.S. in the cyber arena is trying to draw a bright red line," Brookings Institution scholar, Kenneth Lieberthal, wrote in a commentary. "Effectively, the U.S. position is everyone conducts espionage; we don't object to Chinese espionage, they should not object to ours. But, the U.S. does not do commercial espionage to benefit our own firms competitive position, the Chinese side does and we insist that they stop."

Administration officials said the two sides discussed Monday international law and norms in cyber space, and both made practical proposals to increase cooperation and transparency, but the officials gave no details. The U.S side said it raised cyber-enabled theft of intellectual property, trade secrets and confidential business information for economic gain. On Tuesday, officials will also discuss maritime security, missile defense and nuclear policy.

Chinese Ambassador to the U.S., Cui Tiankai, on Sunday rejected allegations of Chinese hacking. He told Chinese journalists that Washington has failed to present hard evidence to prove it, state news agency Xinhua reported. He referred to Snowden's revelations about U.S. cyber surveillance and spying against China and other countries and said it demonstrated cyber security is a global problem faced by most countries.

The ambassador proposed creating common rules for cyber space through the United Nations, Xinhua said.