US Deputy National Security Advisor John Brennan met with Yemen's vice president on Saturday and expressed Washington's commitment to provide support to the troubled country, official reports said.
"The US will stand side by side with Yemen as it works to emerge from these difficult circumstances," the official SABA news agency quoted Brennan as saying in a meeting with Abdrabuh Mansur Hadi in Sanaa.
It said Brennan, the top US counter-terrorism official, delivered a letter from President Barack Obama to Hadi, expressing a firm "commitment to providing all forms of support and assistance" to the Arab world's poorest country.
Brennan's visit came just three days ahead of Yemen's presidential poll in which Hadi, the only candidate, is to replace veteran leader Ali Abdullah Saleh who is stepping down after 33 years in power.
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Saleh agreed to a Gulf-brokered and US-backed power-transition deal after months of mass protests demanding his ouster.
The violence and political deadlock that engulfed Yemen since January 2011 left hundreds dead and thousands more wounded. It has also crippled Yemen's already weak economy and pushed millions of Yemenis further into poverty.
The deteriorating security situation has raised alarm including at the UN Security Council of a growing presence of Al-Qaeda militants in lawless areas in the south and east of Yemen.
In mid-January, the extremists made a significant advance towards the capital Sanaa when more than 1,000 Al-Qaeda fighters swept into the town of Rada and held it for nine days.
The United States and Yemen were once close anti-terror allies, with the US funnelling millions of dollars in aid to Saleh's government to help quell the growing influence of the extremist group.
That support has slowed since the mass protests and brutal crackdown.