The United Nations Security Council announced it is allowing the mandate for the U.N. observer mission in Syria to expire Sunday, but hopes to establish a political office in the battle-ravaged country.

The council's current president, French Ambassador Gerard Araud, said Thursday that members agreed the conditions for possibly extending the current mission had not been met. U.N. officials estimate that as many as 2.5 million Syrians are in need of assistance because of the violence.

The Security Council's announcement comes a day after a Syrian warplane killed more than 40 civilians and wounded more than 100 others in the rebel-controlled northern border town of Azaz.

Human Rights Watch visited the site Thursday, saying the attack leveled an entire block of houses and may have been targeting two nearby facilities of the rebel Free Syrian Army.

Meanwhile, the United States commended the Organization of Islamic Cooperation for suspending Syria from the 57-member bloc of Muslim nations.

In a statement , State Department spokeswoman Victoria Nuland said the OIC's decision sends a “strong message” to Syrian President Bashar al-Assad's government and shows the Damascus regime is increasingly isolated.

Security Council vetoes by China and Russia blocked earlier attempts to have the U.N. take on a larger role in the Syrian conflict, and ultimately led to Thursday's decision to withdraw the observers. An Assad adviser now visiting China, Bouthaina Shaaban, praised Beijing and Moscow for their reaction to the crisis in Syria. He said China and Rusdsia – unlike the Western powers – are not acting like “colonizers” in Syria.

Shaaban's comments appeared in the state-run China Daily newspaper. He is due to meet with Chinese Foreign Minister Yang Jiechi.

China and Russia's vetoes blocked action on three U.N. Security Council resolutions that would have threatened Syria with sanctions for using heavy weapons against civilians.