..Iraq is enduring the "most dangerous phase" of its modern history, with sectarianism, political tensions and terrorism soaring and the fledgling democracy in jeopardy, ex-premier Iyad Allawi told US media.

And with the last US soldier leaving the war-torn country just one month ago, Allawi said the United States is morally obligated to use its diplomatic muscle to restore "sanity" to Iraq's political landscape.

"Let me tell you frankly, there are lots of problems now. The whole situation is very tense," Allawi said in an interview with the CNN show "Fareed Zakaria GPS" that aired Sunday.

"Sectarianism is coming back in force in this country. I think that Iraq is passing through the most dangerous phase through its history now."

Iraq has been rocked by waves of attacks in the month since US troops pulled out from the country they invaded eight years ago, and concern has soared about Iraqi forces' capabilities to maintain internal security.

On Sunday in mostly Sunni Ramadi a series of attacks and a siege of a police compound left seven policemen dead, one day after a suicide attacker targeting Shiites killed 53 people near Basra.

Nearly 200 people have been killed in the violence in less than a month, as a political standoff in Iraq pits the Shiite-led government against the main Sunni-backed political bloc, stoking sectarian tensions.

Authorities have charged Sunni Arab Vice President Tareq al-Hashemi with running a death squad, and Prime Minister Nuri al-Maliki, a Shiite, has called for his Sunni deputy Saleh al-Mutlak to be sacked.

Allawi, a secular Shiite, is leader of the bloc that won the most seats in 2010 elections, but he backed out of a power-sharing deal with Maliki.

"I have warned in the very early days -- in fact, years ago -- that sectarianism and having a vacuum and having a political process which is not inclusive, can only destroy the future of this country," Allawi told CNN.

He cited US President Barack Obama's claim last month that US forces were leaving Iraq a stable and democratic country.

"It's neither stable nor democratic, frankly speaking," Allawi said. "The terrorists are hitting again very severely, and Al-Qaeda is fully operational now in Iraq."

He stressed that while he did not want a return of US troops to Iraqi soil, Washington should "use its diplomatic and other channels through the strategic agreement between the United States and Iraq to try and bring about sanity to the political process and inclusivity."

The United States, he said, has "a political as well as moral responsibility to help this country to pass through this very difficult phase."