LONDON (AFX) - The yen firmed further against the dollar at midday as it continued to benefit from the instability in the Middle East, dealers said. "Japan has a large current account surplus, and it's accepted that in times of crisis investors want to keep their money at home," Barclays Capital currency strategist Jane Foley said. "That's the only fundamental reason for the yen's rise," Foley said. Given the lack of significant economic figures until Friday's US retail sales, currency movements will for the moment continue to reflect the situation in the Middle East, dealers said. They said that while the dollar is vulnerable to the Middle East crisis, it is not expected to remain weak against the yen for long. The euro has already retreated following yesterday's modest gains on the fall in oil prices and improved German jobless numbers. Analysts have warned that the German figures do not necessarily mean the euro zone's largest economy has turned the corner. In the UK, sterling tracked the euro lower on a similar lack of fresh leads. The release of a study by HSBC showing that financial markets are pricing in roughly a 50 pct chance that the UK will join the euro during the current parliament coincided with signs of mounting opposition within the government to Prime Minister Tony Blair's plans for euro entry.