Washington, Sep 25 (IANS): The US has threatened to slap sanctions on some of the Shia rebels deemed to undermine Yemen's uneasy transition process.

In a phone conversation with Yemeni President Abd-Rabbu Mansour Hadi Wednesday, President Barack Obama's top adviser for counter-terrorism Lisa Monaco reiterated Washington's "strong condemnation" of the Houthi rebels and other parties for use of violence to disrupt Yemen's transition and threaten the country's stability, Xinhua reported.

"She urged all parties to pursue reconciliation and underscored the United States' determination to designate individuals who threaten Yemen's peace, stability and security," the White House said in a statement.

The Yemeni government and the Houthi rebels Sunday night signed a ceasefire deal, ending a week of bloody clashes in the capital city of Sanaa that had claimed more than 400 lives.

The Houthi group, however, refused to sign a security annexe that requires them to hand over towns and cities seized in the past weeks, withdraw fighters from all areas in Sanaa and put an immediate end to protests.

The Houthi fighters, who have tightened their control on most parts of Sanaa after the truce deal was inked, are guarding most of the government institutions.

In her phone conversation with Hadi, Monaco conveyed Obama's "strong support" for the Yemeni leader in his dealing with "recent setbacks" to the country's transition process.

Hadi took office in February 2012 after a power transfer agreement ended the rule of Ali Abdullah Saleh and 11-month mass protests across the country, pledging to carry out reforms during his two-year transitional term, launch a national dialogue with all political factions and combat Al Qaeda in the Arabian Peninsula (AQAP).

The Obama administration had stepped up drone strikes on the AQAP since Hadi took over the presidency, with a view to uprooting the militants in Yemen's southern regions.

Monaco and Hadi pledged to continue cooperation in countering the threat posed by the group.