BEIJING -- Human rights groups are urging U.S. Secretary of State John Kerry to raise the ill-treatment of dissidents and other rights concerns during a weekend visit to China expected to be dominated by talk of North Korea.

The groups said in a letter to Kerry that they fear human rights concerns have been sacrificed as Washington pursues economic opportunities in China and seeks Beijing's support on North Korea, Iran and other international concerns. That harms Washington's overall position with China as the ruling Communist Party feels it is getting the upper hand, they said.

"The Chinese authorities note the soft-pedaling of human rights principles and perceive it as weakness, validating their sense of a changing power dynamic between the two countries and their belief that U.S. human rights policy is more political than principled," said the letter, emailed to reporters in Beijing on Friday.

Seven groups signed the letter, including Amnesty International and Freedom House.

The letter raised no specific cases, but said China in recent years had stepped up repression of political critics and religious dissenters, enacted harsh policies in the western regions of Tibet and Xinjiang, and increased restrictions on civil society, free expression and the Internet.

"The U.S. government response has not elicited meaningful improvements in these areas," the letter said.

"Rather than smoothing the path for co-operation, the United States undermines its interests and compromises its ability to secure progress on other issues when it downplays human rights concerns," it said.

The visit to Beijing is Kerry's first as secretary of state and comes amid rising concerns that North Korea could conduct a missile launch, nuclear test, or direct attack on South Korean and U.S. forces that could seriously destabilize the region. China is the hardline communist regime's strongest political ally, main trading partner and key source of economic assistance, and Washington and others have long hoped Beijing would use its influence to moderate Pyongyang's behaviour.

Rights group have struggled to keep their concerns on the agenda, although the issue featured prominently during a visit by Kerry's predecessor Hillary Clinton last May amid tense negotiations over the status of blind legal advocate Chen Guangcheng, who had taken refuge inside the U.S. Embassy in Beijing. Chen was eventually permitted to leave with his wife and child without causing a major rupture in ties, something heralded by both sides as a sign of greater maturity in the relationship.

The letter was also signed by China Aid, Human Rights in China, International Campaign for Tibet, Reporters without Borders, the Uyghur American Association and the World Uyghur Congress.