BEIJING (AFP) - Moscow and Beijing on Wednesday reaffirmed their strong opposition to intervention in Syria, under mounting international pressure to change a stance that has infuriated Western powers.

A joint statement issued after talks between China's leaders and visiting Russian President Vladimir Putin in Beijing said the two countries opposed any attempt to impose regime change in Syria after 15 months of bloody conflict.

"Russia and China are decisively against attempts to regulate the Syrian crisis with outside military intervention, as well as imposing a policy of regime change, including within the Security Council," it said.

The giant neighbors also came out against any use of military force or "unilateral sanctions" against Iran in the statement, released after China's Premier Wen Jiabao met visiting Iranian President Mahmoud Ahmadinejad.

Wen said Beijing opposes any Middle Eastern country seeking to acquire nuclear weapons, China's official Xinhua news agency reported.

The West believes Iran is trying to develop an atomic bomb under cover of a civilian programme, although Tehran insists its intentions are purely peaceful.

Ahmadinejad is expected to seek support for his country's stance at the two-day summit of the Shanghai Cooperation Organisation (SCO), which was set up in 2001 to allow Russia and China to rival US influence in Asia.

Putin and Ahmadinejad will meet on Thursday, as Moscow prepares to host more talks later this month aimed at finding a diplomatic solution to the standoff over Iran's nuclear ambitions.

Moscow and Beijing have remained in lockstep over Syria, opposing foreign intervention and forced regime change in the conflict-torn nation.

The two nations vetoed two UN Security Council resolutions criticising President Bashar al-Assad's regime earlier this year, but they have also voiced support for UN-Arab League special envoy Kofi Annan's six-point peace plan.

But as Syrian government troops continue to fight armed rebels in a conflict that has now lasted 15 months, doubts have emerged over the effectiveness of Annan's plan, which came into effect mid-April.

Rights groups say more than 13,500 people have died in the Syrian uprising since March 2011, and Western powers are pushing for increased pressure on al-Assad to stop the regime's assault against the population.

On Wednesday Russian Foreign Minister Sergei Lavrov told reporters in Beijing heeding opposition groups' calls for the forcible removal of the Assad regime would lead to "catastrophe" in the conflict-torn state.

He reaffirmed China and Russia's support for the Annan plan, and called for a new international meeting on Syria to include Turkey and Iran.

"We think it is necessary to call a meeting of countries that truly have an influence on various opposition groups," he added, citing the five permanent members of the UN Security Council, the Arab League, the European Union, Turkey and Iran, after meetings with Chinese leaders.

The two countries have also agreed to build military ties, as the United States turns the focus of its huge firepower towards the Pacific -- China's backyard.

"Not long ago in the Yellow Sea, we successfully carried out the first Russian-Chinese joint naval exercise," said Putin during a meeting with China's likely next leader, Vice President Xi Jinping on Wednesday.

"Yesterday, with President Hu, we vowed to continue cooperation in this area."

The giant neighbours have also joined together in resisting Western sanctions imposed on Tehran over its nuclear programme, with China one of the biggest buyers of Iranian oil.

China's President Hu Jintao, speaking in an interview released by the official Xinhua news agency Wednesday, said countries should refrain from escalating the issue of Iran's nuclear programme.

Hu also said China, Russia and other SCO member countries had vowed to play a bigger role in Afghanistan, as NATO forces prepare to pull out.

"We will... play a greater role in the peaceful reconstruction process in Afghanistan," Hu said in an interview published in the People's Daily newspaper, the mouthpiece of the ruling Communist Party.

"The SCO supports Afghanistan becoming an independent, peaceful, prosperous, neighbourly country, free from terrorism and drugs," he said.

Afghan President Hamid Karzai will meet Chinese leaders on the sidelines of the summit, which Afghanistan's foreign ministry says will elevate the relationship between the two countries.