Yemen's president Ali Abdullah Saleh blames recent protests on Israel and the US, accusing them of destabilizing his country and the Arab world as protesters demanding his ouster press ahead with demonstrations.
His comments on Tuesday marked his harshest public criticism yet of the US, a key ally with which his government is battling al-Qaeda pockets in the Arab Peninsula.
He said "there's an operations room in Tel Aviv with the aim of destabilising the Arab world" and that it is "run by the White House".
There was no immediate reaction to Saleh's comments from Washington.
An hour after Saleh's speech, tens of thousands of protesters marched to the capital's university, joined for the first time by opposition parties.
Sheikh Abdul-Majid al-Zindani, a cleric the US accuses of having links to al-Qaeda, was present at the gathering and declared his support for the protesters.
Saleh, speaking to faculty at Sanaa University, accused the US president of meddling in the Middle East. "Mr Obama, you're the president of the United States; you're not the president of the Arab world," he said.
Protesters pressed ahead with demonstrations despite an offer a day earlier from the president to form a unity government. Ali Abdullah Saleh has been in power since 1978.
Tuesday's protest is the latest in a series that have rocked the country for weeks and claimed at least 24 lives.
The protesters chanted one word: "Leave", in reference to Saleh who until Monday was reluctant to address their demands and said they could not achieve their goal through "anarchy and killing".
But on Monday Saleh appeared to back down, saying he would accept members of the opposition in a new government if the protesters stopped their demonstrations.
The offer was swiftly rejected by both opposition figures and protesters who described it as an outdated "tranquiliser".
Many protesters are angry at widespread corruption in a country where 40 per cent live on $2 a day or less and where university graduates without connections struggle to get jobs. Youth unemployment is rampant.
Yemen is also riven with regional strife, with Shia rebels in the north and separatists in the south demanding fairer political participation.
