President Barack Obama's top counter-terrorism advisor called President Abdrabuh Mansur Hadi on Wednesday to condemn Shiite rebels the Yemeni leader says have brought his country to the brink of civil war.
The advisor, Lisa Monaco, also offered strong support for Hadi as he confronts "setbacks" in Yemen's political process, the White House said.
Yemen's Shiite Huthi rebels have seized key institutions in the Red Sea nation.
"Ms. Monaco reiterated the United States' strong condemnation of members of the Huthi movement and other parties who have resorted to violence to disrupt Yemen's peaceful transition and threaten the country's stability," the White House said in a statement.
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The Huthi rebels waged a decade-long insurgency in the mountainous north of Yemen before launching a bid for power in Sanaa in August.
Hundreds of them have set up checkpoints and have been seen in the capital guarding government offices and army bases alongside troops.
Hadi warned earlier Wednesday that the rebel advances in Sunni-majority Yemen were in danger of dragging the country towards civil war and accused "foreign forces" of seeking to derail a political transition that sprung from an Arab Spring uprising.
Yemeni authorities accuse Iran of backing the rebels, who are alleged to be influenced by Lebanon's powerful Shiite militia Hezbollah, which is backed by Tehran.
Monaco told Hadi that the United States would designate for sanctions any individual guilty of overthrowing Yemen's peace and security.
She also reiterated that Washington and the Hadi government would continue to work together to address the threat from Al-Qaeda in the Arabian Peninsula (AQAP), which is based in Yemen and has plotted attacks against US targets, including civilian aircraft.