The first chief US diplomat to visit Yemen in more than 20 years, US Secretary of State Hillary Clinton said the trip was aimed at going beyond military cooperation to broach a "comprehensive strategy" for tackling Yemen's myriad problems.
The US embassy in the Yemeni capital Sanaa said that Clinton had arrived in the country for a half-day visit "bearing the message of a 'long-term partnership'."
She would meet President Ali Abdullah Saleh to "exchange views on emerging issues and discuss common interests," said an embassy statement.
Saleh's government is fighting not just Al-Qaeda in the Arabian Peninsula (AQAP), but also rebels in the north, secessionists in the south, as well as an acute water shortage, vanishing oil revenues and a deep economic crisis.
US-based analysts fear Yemen's problems are so serious the country risks becoming a failed state like Somalia and allowing Al-Qaeda to take a firm grip on both sides of the world's oil shipping lanes in the Gulf of Aden.
"Yemen is increasingly a very strong partner in our counter-terrorism efforts," Clinton said in a briefing to reporters before undertaking a trip given tight security.
However, she acknowledged the limits of such cooperation.
"It's not enough to have military-to-military relations," she said earlier on a five-day tour of the Gulf Arab region. "We need to try to broaden the dialogue."
Much as it has been doing for years in Afghanistan and Pakistan -- the front line on the war against Al-Qaeda -- the United States has in past months boosted development assistance as well as military aid.
Washington says it is running programmes aimed at increasing jobs, helping farmers, building schools and improving health care for Yemenis who lack adequate services in remote regions.
General public interest in Yemen has grown since a botched bid on Christmas Day 2009 to blow up a US airliner over Detroit by a Nigerian passenger allegedly trained by the Yemeni-based AQAP.
The group has also taken credit for a foiled air cargo bomb plot in October, in which printer toner cartridges that had been rigged as bombs were shipped from Sanaa and, according to investigators, set to explode over the United States.
One of the leaders of the group -- Anwar al-Awlaqi, a US-Yemeni citizen believed at large in the vast and lawless tribal areas -- is now viewed as a threat on a par with Al-Qaeda leader Osama bin Laden.
Although the State Department had sought to keep the visit closely under wraps, the Yemeni Post, an English-language newspaper, reported Clinton would pay a four-hour visit on Tuesday.
She would meet leaders of the opposition JMP Party in a bid to defuse tension between them and the ruling party over the election and amendments the latter wants to pass, the newspaper said.
In her meeting with Saleh, Clinton will likely use efforts at damage control after leaked US diplomatic cables alleged Yemen's president admitted lying to his own people by pretending US military strikes against Al-Qaeda are carried out by his own forces.