(CNN) -- A Syrian jihadist group appears to have pledged allegiance to al Qaeda's leader -- but also stressed it can achieve a Syrian Islamic state only by working with other rebels, including secularists.
The group, al-Nusra Front, also denies an earlier claim that it has merged with Iraq's al Qaeda affiliate, according to an audio message purported to be from al-Nusra general commander Abu Muhammad al-Joulani.
The message was posted on various radical Islamist websites known for posting similar statements by al Qaeda figures.
Al-Joulani's message comes after the leader of the al Qaeda-affiliated Islamic State of Iraq purportedly claimed this week in an audio statement that al-Nusra Front is part of its network.
A speaker identifying himself as Islamic State of Iraq leader Abu Bakr al-Baghdadi had said -- in a message posted to online jihadist forums -- that the two groups would combine their names and be known as "The Islamic State of Iraq and the Levant (Syria)."
But al-Joulani distanced himself from al-Baghdadi's message, saying it took al-Nusra off guard.
"We would like to inform the public that we were not informed or consulted of the content of the announcement," al-Joulani said.
Despite denying a merger, al-Joulani said that he is raising the bar higher by pledging allegiance to al Qaeda leader Ayman al-Zawahiri.
Still, such a pledge "will not change the policies of Nusra Front on the ground," al-Joulani said.
He said the group's goal of achieving an Islamic state in Syria "can only be built with the help of everyone -- without excluding any of the main parties who bled and fought with us and waged jihad in Syria."
Al-Joulani said that includes "all the other rebel factions."
Al-Joulani, acknowledging that al-Nusra Front fought with jihadists in Iraq before turning its attention to the Syrian civil war, said he would delay consideration of a merger with al Qaeda in Iraq in part so his group can consult with various supporting groups.
The U.S. State Department labeled al-Nusra Front a foreign terror organization linked to al Qaeda in Iraq back in December.
Moaz al-Khatib, president of the main Syrian opposition alliance, said this week on his official Facebook page that al Qaeda's way of thinking "does not suit us."
Al-Khatib heads the National Coalition for Syrian Revolutionary and Opposition Forces, which has leadership largely consisting of expatriates. He said that "there are those who want to impose themselves even on al-Nusra Front."
"We reject ownership of any of the rebel factions inside Syria," he said.
Al-Joulani's message comes a week after the White House, according to U.S. officials, signed off on new nonlethal aid for Syrian rebels. Officials said it is expected to include equipment such as body armor, night vision goggles and other military equipment that is defensive in nature, but could be used to aid in combat by Syrian rebels battling forces loyal to President Bashar al-Assad.
Syrian opposition leaders asked for more aid, including lethal aid, at a meeting with U.S. Secretary of State John Kerry in London on Wednesday, according to two senior State Department officials who briefed reporters on condition of anonymity. But the requests weren't specific, and Kerry didn't make any promises, the officials said.
Kerry urged the opposition to work together and organize more effectively, the officials said. Opposition officials said they were in the process of doing that.
Meanwhile, Kerry, who also discussed Syria with Russian Foreign Minister Sergei Lavrov, will head to Turkey on April 20 for more talks with European and Persian Gulf states on the crisis, the officials said.
President Barack Obama agreed last month to send food and medicine to the rebels, the first direct U.S. support for the armed opposition. But the package falls short of the heavy weapons and high-tech equipment sought by the rebels.
The decision also comes as Britain and France are leading efforts to lift a European Union arms embargo on Syria. Both have suggested they are prepared to join nations like Qatar in providing the rebels with weapons and are urging the United States to do the same.
The United Nations says more than 70,000 people have been killed in Syria's two-year civil war. Opposition activists reported at least 75 more deaths on Wednesday amid heavy fighting in and around Damascus and Daraa.
CNN's Hamdi Alkhshali and Elise Labott contributed to this report.