U.S. State Secretary Hillary Clinton said on Wednesday that the Arab League (AL) monitoring mission in Syria should not continue indefinitely, slamming the recent speech by Syrian President Bashar al-Assad as "chillingly cynical."

"I think that it's clear to both the prime minister and myself that the monitoring mission should not continue indefinitely," Clinton told reporters at the State Department alongside visiting Qatari Prime Minister and Foreign Minister Sheikh Hamad bin Jassim al-Thani.

"We cannot permit President Assad and his regime to have impunity. Syrians deserve a peaceful transition," she said.

Clinton said the United States was looking forward to work with the AL when the current monitoring mission expires on Jan. 19, without specifying what actions the United States planned to take.

In response to Assad's fourth speech since the eruption of unrest in Syria in mid-March, she sharply criticized it as " chillingly cynical."

Instead of taking responsibility, the speech was "only making excuses, blaming foreign countries, conspiracies so vast that now it includes the Syrian opposition, the international community, all international media outlets, the Arab League itself," said Clinton.

Assad, in his Tuesday speech at the Damascus University, vowed to fight the "terrorists" in his country with an "iron fist," accusing them of working to pave the way for foreign interventions.

Saying he would not give up responsibility so long as he still has the support of his people, the embattled president pledged that his country would not close door to any Arab solution that respects the Syrian sovereignty and the independence of the country's decision.

Clinton said that the AL monitors, who arrived in Syria two weeks ago, were trying to judge whether the country was keeping its promise to end the killings, withdraw its troops and release political prisoners.

"So far, the regime has not done so," she concluded.

"It claims to have released some prisoners, but thousands more are still not free. Dozens more are arrested every day," said Clinton.

"We've seen the Syrian army paint its assault vehicles blue to disguise military forces as police to hide from the world the full extent of its crackdown," she added.

Syria signed an AL observer protocol on Dec. 19 last year in the Egyptian capital of Cairo after the pan-Arab body threatened to take the issue to the UN Security Council.

As of Sunday, there are all together 165 observers monitoring the situation in Syria as part of an AL peace initiative to end the months-long turmoil there.