Yemeni President Ali Abdullah Saleh declared Thursday that he would not step down as long as his key rivals remain in influential positions, potentially dashing U.S. hopes for a peaceful transition of power.

Saleh also said that the United States was playing a previously unknown role in assisting Yemeni forces fighting an al-Qaeda affiliate in southern Yemen, underscoring U.S. concerns that the political vacuum here could allow Islamist militants to deepen their grip and create a haven from which to attack the United States and its allies.

Saleh made his comments in a nearly 20-minute interview with The Washington Post and Time magazine Thursday. It was his first interview since his return to Yemen last Friday from Saudi Arabia, where he was treated for burns and other injuries suffered in a June attack on his presidential compound in Sanaa.

On Thursday, Saleh sat in a large room inside the compound, along with top advisers. Deep scars marked his face. He wore a traditional tribal headdress and gold-colored medical gloves, the type typically worn by burn victims. He appeared in good health and spirits, smiling and peppering the conversation with doses of humor.

Saleh said that a political transition plan crafted by Yemen’s Persian Gulf neighbors made clear that “all elements” causing tensions in Yemen need to be removed. That meant his main rivals — Maj. Gen. Ali Mohsen al-Ahmar, who turned against Saleh and joined the nation’s now eight-month-old populist uprising, and the Ahmar clan, a powerful tribal family not related to the general — could not be allowed to run for elections or hold political office or a military command if he steps aside, Saleh said.

“Because if we transfer power and they are there, this will mean that we have given into a coup,” he said. “If we transfer power, and they are in their positions, and they are still decision-makers, this will be very dangerous. This will lead to civil war.”

Saleh’s defiant stance underscored the deepening animosities between him and his rivals, which could torpedo the gulf Arab initiative. Hamid al-Ahmar, the tribal family’s billionaire scion who has expressed interest in the presidency, wields enormous political power in the main opposition coalition, the Joint Meeting Parties. Mohsen, once Saleh’s confidant and strongest ally, still commands much of Yemen’s military and is revered by his soldiers.

Their forces engaged in fierce clashes against forces loyal to Saleh and his family last week; more than 150 people were killed and scores injured — mostly youth activists who seek to end the president’s 33-year-long rule. On Thursday, tribesmen loyal to the Ahmars clashed with tribesmen loyal to Saleh in the capital’s Hassabah enclave.

The violence has been accompanied by an escalation in sharp rhetoric in recent days between Yemen’s warring sides, ratcheting up tensions in this Middle Eastern nation, the region’s poorest.

On Thursday, Saleh strongly hinted that Mohsen and the Ahmars, along with Yemen’s political opposition, might have played a role in the attempt to assassinate him. The government, he said, is waiting for the results of a U.S. investigation into the attack, which Saleh said could be completed by the end of the month.

If Mohsen and the Ahmars are implicated in the attack, they would face prosecution, Saleh vowed.

When asked why government security forces were violently suppressing protesters with heavy machine guns, mortars and snipers, he blamed Mohsen and the Ahmars.

“They are the ones who attack the military bases, the civilians and the protesters — the protesters that are moving around the city with the protection of Ali Mohsen and the Ahmars, using armed people. And they assassinate protesters from behind so they can blame the state,” Saleh said.

In a telephone interview, Mohsen denied the allegations, calling Saleh “a liar” who could not be trusted.

“His return to the country shows that he carries with him a revengeful soul,” Mohsen said. “Unfortunately, the president is not absorbing that the whole nation is incapable of living with him.”

Several members of the Ahmar family could not be reached for comment, but they have in the past denied Saleh’s allegations and have been equally critical of his rule. Hamid al-Ahmar was the first prominent figure to demand that Saleh step down.

Despite lashing out at his rivals, Saleh reiterated that he was still committed to the gulf Arab initiative. He denied that he was stalling in order to remain in power. He said that Yemen’s vice president, whom he authorized to negotiate with the Joint Meeting Parties, was waiting for the opposition to be more flexible.

“This is a misunderstanding. We are willing within the next hours and next days to sign it, if the JMP comes closer” to reaching an agreement, Saleh said. “We don’t want to prolong it. And we don’t want this crisis to continue.”

Still, Saleh warned that he was not prepared to leave Yemen without a stable transition of leadership. “What is important to [the JMP] is to remove the president from power and the country would then go through chaos,” he said.

He branded the opposition, especially al-Islah, Yemen’s largest opposition party, which includes members of the country’s Muslim Brotherhood, as Islamists who support al-Qaeda-linked militants. JMP officials have denied the allegations.

On several occasions, Saleh mentioned the U.S.-Yemeni counterterrorism alliance. “We are fighting the al-Qaeda organization in Abyan in coordination with the Americans and Saudis,” he said without elaborating.

Yemeni forces are engaged in fierce battles to retake territory lost to al-Qaeda-linked militants, who have taken over large swaths of the southern province of Abyan, including its capital, Zinjibar.

Saleh also warned the United States, which has denounced the violence and called for him to step down soon, to be patient.

“I am addressing the American public. I want to ask a question: Are you still keeping your commitment in continuing the operations against the Taliban and al-Qaeda?” he asked. “If yes, that will be good. But what we see is that we are pressed by America and the international community to speed up the process of handing over power. And we know where power is going to go. It is going to al-Qaeda, which is directly and completely linked to the Muslim Brotherhood.”

Special correspondent Ali Almujahed contributed to this report.