Syrian officials said the league's proposals weren't in the best interests of the people and would interfere with internal governance, the BBC reported Monday.
One official said Syrians have "rallied around" Assad during the unrest in the country.
The Arab League urged Assad to step down as part of a timetable for a transition of power, Britain's Guardian reported.
Proposals made at an Arab League meeting in Cairo Sunday call for negotiations between the government and the opposition within two weeks and the establishment of a national unity government within two months, The Washington Post reported. They also called for Assad to transfer power to his deputy and multiparty elections observed by international monitors within three months.
In addition, the proposals would extend the Arab League monitoring mission for one more month and call on both sides to end the violence.
Saudi Arabia said it plans to pull its Arab League monitors from Syria, with Saudi Foreign Minister Saud al-Faisal accusing the Syrian regime of acting in bad faith and not implementing any of its obligations n the Arab League resolution that set up the monitoring mission, The Guardian reported.
"My country will withdraw its monitors because the Syrian government did not execute any of the elements of the Arab resolution plan," he said.
The foreign minister implored league members to enforce economic sanctions the league adopted against Syria in November but which few members have undertaken.
He also called on the international community to "bear its responsibility," including "our friends in Russia, China, Europe and the United States" as well as "our brothers in Islamic states." That responsibility includes applying "all possible pressure" to compel Syria to comply with the Arab peace plan.
The Local Coordination Committee in Syria, an opposition group, said the league's proposals were "unattainable" and its mission should be declared a failure.
In a statement, the organization said the Syrian people have lost confidence "in the Arab League's ability to stop the regime's ongoing bloodshed. It is clear that the regime has been pulling the country towards chaos and destruction while the Arab League remains stagnant."
The organization said it considered the extension as "another deadline for the regime's killing machine and a form of support in suppressing the Revolution while Syrian society is being obliterated."
The LLC said 795 people died since the monitors came to Syria. The United Nations last month estimated more than 5,000 deaths since mid-March. Opposition groups estimate more than 6,000 people have died.
In Cairo, Mohammad Ahmad Dabi, the Sudanese general in charge of the Arab League's monitoring mission, said during a news conference the level of violence has fallen since the observers' arrival in December.
Dabi said reports conflicted about the number of political detainees in Syria.
Activists have criticized Dabi after he said observers saw "nothing frightening" in Homs, which has seen some deadly confrontations between pro-democracy factions and government forces.
The BBC has called for an apology from Syrian state TV after it accused the British broadcaster of fabricating stories and fomenting tensions.
BBC foreign editor Jon Williams tweeted: "BBC demanding apology from #Syria's Al Dunya & Al Ikhbaria TV: accused us of inciting sectarianism & fabricating stories. Of course, untrue."
Williams also alleged a BBC employee was attacked by Assad supporters.
Activists blame the violence on Assad regime forces and the government says terrorists are responsible for the bloodshed.
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