WASHINGTON - Iran and Afghanistan will dominate talks by U.S. Secretary of State Hillary Clinton next week on a trip to Britain and Russia that could also spur progress on a new nuclear arms reduction treaty with Moscow.

Clinton leaves on Friday for a European tour that includes a stop in Switzerland to commemorate an accord between rivals Armenia and Turkey as well as a visit to Dublin and Belfast to support peace in Northern Ireland.

The meatiest portion of the trip will be in Russia.

Clinton, who has sought to reset U.S. ties with the Kremlin, said she was encouraged by Moscow's role in talks with Britain, China, France, the United States and Germany -- dubbed the P5+1 -- on curbing Iran's nuclear ambitions.

The cooperation that we are seeing from our Russian partners in the P5+1 context is very encouraging, she told reporters on Thursday, adding Iran would be a topic next week.

We will certainly be looking at the options that we have to explore going forward from what was a positive but not conclusive meeting in Geneva, she said.

The six world powers recently held talks with Iran in Geneva, which officials described as constructive. Russia has been traditionally reluctant to impose sanctions on Iran.

Several other issues will also feature in Clinton's talks with Foreign Minister Sergei Lavrov and Russian President Dmitry Medvedev. Analysts believe a recent U.S. decision to revamp plans for a missile defense shield in Europe will aid both nations in working together on a host of issues.

The 'reset' is happening, said Steven Pifer, a Russia expert at the Washington-based Brookings Institution.

While there are still a lot of difficult issues in the U.S.-Russia relations, at this point you have some positives that weren't there at the end of 2008.

Many areas still rankle.

A State Department official said Clinton would broach human rights and Russia's treatment of Georgia, with which it fought a five-day war last year. Moscow recognized South Ossetia and another rebel province, Abkhazia, as independent states.

Clinton will also press for more help in Afghanistan after Russia recently allowed the United States to fly weapons, hardware and personnel across its territory to that country, where insurgent violence has reached its highest levels of the eight-year war.

The Russians could provide more assistance to Afghanistan including ... in the form of weapons for the Afghan army, training, counternarcotics, the official said.

ARMS IN RUSSIA, PEACE IN NORTHERN IRELAND

The top U.S. diplomat hopes to advance talks to replace the Strategic Arms Reduction Treaty, which expires on December 5. President Barack Obama and Medvedev agreed on the outlines of a deal in July, but several hurdles may make it difficult to finish by the December deadline.
The secretary will also fly to Kazan in Russia's Republic of Tatarstan to illustrate the U.S. desire to engage with Russians across the country.

Before going to Russia, Clinton, whose husband, Bill Clinton, took a major role as president in the push for peace in Northern Ireland, will visit Belfast and Dublin.

The trip, her first there as secretary of state, shows the former first lady's commitment to resolving remaining issues related to Northern Ireland's peace process, the State Department official said.

Northern Ireland has enjoyed relative peace since a 1998 peace deal between pro-British Protestants and minority Roman Catholics who now share power in a regional assembly. But hard-line splinter groups remain a threat and dissident republicans have stepped up attacks on police.

I think this is sort of the Clinton family signature foreign policy issue, said Heather Conley, a European affairs expert at the CSIS think tank.

Clinton will also meet with British Prime Minister Gordon Brown in London to discuss Afghanistan and Iran, while reassuring some anxious Britons about the strength of the special relationship between their two nations.

These consultations will underscore the strength of the UK-U.S. relationship and the continuous high-level engagement we enjoy with our friends and allies, Assistant Secretary Phil Gordon told reporters.

(Editing by Peter Cooney)