LONDON (AFP) - US Secretary of State John Kerry on Monday appealed to the Syrian opposition to reconsider their decision to boycott talks with foreign powers in Rome this week.

"I would urge the Syrian opposition to join us," Kerry told a news conference in London after talks with British Foreign Secretary William Hague at the start of his first overseas trip since taking office.

"I want our friends in the Syrian opposition council to know that we are not coming to Rome simply to talk. We are coming to Rome to make a decision on next steps," he said.

He stressed however that the US continued to pursue a political resolution to a conflict which the United Nations believes has cost the lives of more than 70,000 people.

The Syrian National Council has said it will pull out of the Friends of Syria talks in the Italian capital on Thursday in protest at the international community's "shameful" inability to halt the bloodshed.

But Kerry argued: "We think it's important to get together to hear directly from the opposition to know precisely what they think would be most useful at this point in time, how we can make a difference.

"I think it's an important meeting... and I still remain hopeful they will make the decision to come and join us."

Kerry, who is conducting a nine-country tour of US allies, said the killings in the Syrian city of Aleppo last week were "further evidence" that President Bashar al-Assad must stand down.

"The Syrian people deserve better than the horrific violence that now invades and threatens their everyday lives," Kerry said.

From London, Kerry goes on to Berlin where he will hold talks on Tuesday with his Russian counterpart Sergei Lavrov, when he is expected to push Moscow to put pressure on the Syrian regime to allow a "political transition".

Russia is one of the few major powers who still maintain ties with Assad's regime.