US Secretary of State Hillary Clinton leaves a diplomatic crisis in China for a difficult mission in Bangladesh on Saturday where violence and a crackdown on the opposition threaten new instability.

Clinton, set to sign a new partnership agreement, is the first US secretary of state to visit Bangladesh since Colin Powell in 2003 amid chronic political infighting in the world's third largest Muslim-majority country.

The last few weeks have seen rallies and strikes over the disappearance of regional opposition figure Ilias Ali in mid-April, who supporters say was abducted by security forces. Four people have died in the unrest.

Following a rally in the capital last weekend and a series of explosions at a government building complex, police have since charged and arrested a number of senior figures from the opposition Bangladesh Nationalist Party (BNP).

A US official said that Clinton would meet Saturday with both Prime Minister Sheikh Hasina and BNP leader Khaleda Zia, who have dominated Bangladesh's politics for decades and whose mutual dislike is as intense as it is personal.

The official said Clinton would promote democracy and good governance but look to broader interests with Bangladesh, a US partner in counter-terrorism efforts and the world's largest contributor to UN peacekeeping.

"Secretary Clinton's trip is an opportunity to take the bilateral relationship to a new level with this moderate, tolerant, democratic, Muslim-majority nation that offers a viable alternative to violent extremism," the State Department official said on customary condition of anonymity.

Bangladesh is "a voice for regional stability in a troubled region," the official said.

Analyst Manzur Hasan, a professor of Brac University in Dhaka, believes Clinton will press Hasina over governance problems in the notoriously corrupt and politically unstable country.

"She is arriving at an awkward moment in a situation of political turmoil when the country is facing some serious issues and difficulties because of the return of the confrontational politics and street protests," he told AFP.

Recent problems for Muhammad Yunus, Bangladesh's only Nobel peace prize winner and a personal friend of Clinton and her husband Bill, will be another thorny issue for the secretary of state to address in her meetings.

Yunus was forced out of his ground-breaking micro-credit bank last year and has since claimed he is the victim of a vendetta that will result in the government seizing his empire of social businesses aimed at alleviating poverty. Clinton will meet Yunus on Sunday, the US official said.

In Dhaka, the government has talked up Clinton's visit as an event that will take ties to "a new height".

"It will be a new beginning of bilateral relations between the two countries," Foreign Minister Dipu Moni said on Thursday. "Her visit is extremely important for Bangladesh."

Moni told reporters Dhaka would press for lower tariffs on its exports to the US, its largest market, and the two nations were in the final stage of signing an agreement to boost economic ties.

Gowher Rizvi, international affairs adviser to the Bangladeshi prime minister, told AFP the partnership dialogue would be "similar to the ones the US have with India and China".

Clinton's trip to China has been overshadowed by a row over blind Chinese dissident Chen Guangcheng who fled to the US embassy last week.

US officials said Friday that Beijing had agreed to let Chen leave for the United States, after a controversial initial deal under which the activist left US protection with promises for his safety inside China.

Clinton is due to leave Dhaka on Sunday for the eastern Indian city of Kolkata and then proceed to New Delhi for talks on expanding an alliance that has grown in its importance but is widely seen as having failed to blossom.

kk-sa-adp-sct/mtp