Britain will look into imposing new financial, energy and transport sanctions on Syria over its harsh crackdown on protests but Russia may hold the key to increasing pressure on President Bashar al-Assad, a minister said on Thursday.

European Union countries, including Britain, have slapped several rounds of sanctions on Assad's government since May over its violent suppression of unrest, including an embargo on Syrian oil and a ban on new investment in the energy sector.

We will continue to look for new ways in energy, in transport, as well as financial restrictions, to put pressure on the Syrian regime, Foreign Office Minister Alistair Burt told Reuters in a telephone interview.

Britain would look at these possible new sanctions through the EU, and if we get the chance through the United Nations as well, said Burt, the Foreign Office minister responsible for the Middle East and North Africa.

One of the triggers though may be Russia. Russia, I think, is getting increasingly isolated in its reluctance to use its leverage against Syria, he said.

Russia and China used their veto power as permanent U.N. Security Council members in October to block passage of a Western-drafted resolution that would have condemned Syria's government over the crackdown.

We continue to talk with them (Russia) about what more they can do. If they are not willing to back U.N. sanctions, what are they willing to do? We will continue to use whatever leverage we can because the killing must stop, Burt said.

Russia, a major arms supplier to Syria, has called Western criticism of its actions against Damascus in the U.N. Security Council immoral.

Navi Pillay, the U.N. human rights chief, said this week that the death toll in nine months of unrest in Syria had exceeded 5,000.

NEW IRAN SANCTIONS LIKELY

Burt also said he expected EU foreign ministers to agree to impose new sanctions on Iran at their next meeting in late January, but that he did not know whether they would agree to an embargo on Iranian oil. Britain is supportive of an EU ban on imports of Iranian oil, he said.

Iran faces increasing international isolation over its nuclear energy programme the West believes is aimed at yielding atomic bombs. Tehran says the programme is wholly peaceful.

I think the sanctions to date are proving to be successful. We know Iran is becoming increasingly desperate to finance its nuclear programme. The banking and financial restrictions are having an impact but we believe that more could and should be done and we will be pressing for this, Burt said.

Britain shut Iran's embassy in London and expelled all its staff after the British Embassy in Tehran was attacked last month by a crowd angry at sanctions imposed by Britain. Britain closed the Tehran embassy and evacuated its staff.

Burt said it was too early for Britain to set any conditions for re-establishing normal diplomatic relations with Iran.

We genuinely feel this is not up to us. It was them who ransacked and destroyed our embassy ... I don't think it is for the United Kingdom to start making overtures to Iran and we have no intention to do so, he said.

Although Britain was not discussing bilateral issues with Iran at present, it wanted to keep channels open for participating in multilateral talks with Iran, particularly on the nuclear issue, he said.

He said he hoped talks between Iran and six major powers, including Britain, on Tehran's nuclear programme could resume but the ball is in the Iranians' court. The last round of talks, in January, failed even to agree on an agenda.