Syria's President Bashar al-Assad has said his country will not bow down to "pressure" and predicted its bloody conflict would continue. Speaking to the UK's Sunday Times, he said the unity and stability of Syria were at stake. An Arab League deadline for Syria to end its crackdown passed overnight with no sign of violence abating. There are reports of a grenade attack on a building of the ruling party in the capital Damascus. If confirmed, it would be the first such attack reported inside the capital since the uprising began in March. At least 27 people were killed on Saturday, according to opposition activists, including four government intelligence agents whose car was ambushed in Hama by gunmen believed to be army defectors. Foreign journalists are unable to move around Syria freely, making it difficult to verify reports. The UN believes at least 3,500 people have been killed in the conflict since March. Election promise The Arab League's plan has been the focus of efforts to find a diplomatic solution and comes as key international players such as Russia and the US warned of the danger of civil war in Syria. Syria was reported to have agreed in principle to accept the Arab League's peace plan but critics accused it of stalling for time. "The conflict will continue and the pressure to subjugate Syria will continue," Mr Assad told the Sunday Times. "However, I assure you that Syria will not bow down and that it will continue to resist the pressure being imposed on it." Mr Assad appeared to dismiss the Arab League plan, the BBC's Jim Muir reports from Beirut. He said it was designed to show that the Arabs were divided, and to prepare the way for outside military intervention which, he repeated, would have dire consequences for the whole region. The head of the Arab League said it was studying a letter from Syria seeking changes to its proposed observer mission, with reports saying Damascus is seeking to reduce the observer delegation from 500 to 40. Observers are supposed to oversee the implementation of the plan, which requires the government to stop attacking demonstrators, pull its military out of restive areas and begin negotiations with the opposition. Speaking to the Sunday Times, the Syrian president also promised elections in February or March when Syrians would vote for a parliament to create a new constitution, which would in turn determine future presidential elections. "That constitution will set the basis of how to elect a president, if they need a president or don't need him..." he said. "The ballot boxes will decide who should be president." 'Message to regime' The opposition Local Co-ordination Committees (LCC) said "several" RPG rockets had been launched at a Baath Party building in the Mazraa neighbourhood of Damascus, and firefighters had been dispatched to the area. Normal movement resumed in the streets around the party office on Sunday morning but security forces remained in force inside the building, a BBC reporter says. Our reporter saw no signs of damage to the building but adds that residents reported an exchange of fire overnight. An unnamed witness told Reuters news agency the attack had happened before dawn and the building had been mostly empty. "I saw smoke rising from the building and fire trucks around it," he told Reuters. "It seems to have been intended as a message to the regime." The Syrian Free Army, comprised of army defectors and based in neighbouring Turkey, said it had carried out the attack, according to Reuters. Our correspondent in Beirut says that the report of the grenade attacks is so far unconfirmed and there is even a slight suspicion that it might have been the regime itself doing something to justify its assertion that it is armed terrorists who are behind all the trouble.