Syrians inspect burned cars at the site of a blast in the Syrian capital Damascus Thursday June 28, 2012. A strong explosion rocked the Syrian capital Thursday near a busy market and the Palace of Justice, sending black smoke billowing into the sky. State TV reported at least three people were wounded and around 20 cars were damaged. Image Credit: AP

Riga, Latvia: US Secretary of State Hillary Rodham Clinton says it is "very clear" that all the participants in Saturday's meeting on Syria — including Russia — are on board with a transition plan created by international envoy Kofi Annan.

Clinton spoke Thursday after Russian Foreign Minister Sergey Lavrov said his country would not endorse a call for Syrian President Bashar Al Assad to give up power.

He also denied a claim by a senior US official that Russia was among the backers of a plan for a new Syrian government.

Clinton told reporters that the invitations to Saturday's meeting in Geneva made clear that representatives "were coming on the basis of (Annan's) transition plan".

She said she expects the meeting "to provide an opportunity to make real progress" on that plan.

Turkey builds military presence at Syria border

Clinton's comments followed news that Turkey has sent missile batteries, tanks and troops to the border with Syria as a “security corridor,” after Syrian shot down a Turkish military jet last on Friday, media reports said.

There was no official confirmation, but state-run TRT television showed dozens of military vehicles loaded with army personnel reportedly on the move for the volatile border, in a convoy that included low-altitude air defence systems and anti-aircraft guns.

About 30 military vehicles accompanied by a truck towing missile batteries left a base in the southeastern province of Hatay for the border, about 50 kilometres (30 miles) away, the Milliyet newspaper reported.

The Turkish Phantom F-4 jet was downed by Syrian fire over the eastern Mediterranean in what Prime Minister Recep Tayyip Erdogan said was a “heinous attack” in international waters.

Meanwhile, twin bombs exploded outside the Palace of Justice in Damascus on Thursday as deadly violence raged across the country and Turkey deployed missile batteries along its border with Syria. With fighting in the 16-month-old revolt increasingly focusing on the capital, world powers were preparing for a crucial meeting on ways to end the conflict and to discuss a plan by peace envoy Kofi Annan for an interim government.

The meeting in Geneva, only agreed after wrangling between Moscow and Washington over the agenda and the guest list, is to be attended by some regional governments but not by rival Middle East heavyweights Iran and Saudi Arabia.

Russia poured cold water on Saturday’s meeting, with Foreign Minister Sergei Lavrov saying Moscow backs a political transition in Syria but rejects Western pressure for the ouster of President Bashar Al Assad.

Meanwhile, the UN refugee agency doubled its forecast for the number of refugees who will flee Syria this year to 185,000 and said it would need more than twice as much money as previously thought, the UN coordinator for Syrian refugees Panos Moumtzis said.