The dollar firmed against its peers on Friday, supported as an improvement in investor risk appetite lifted equities and pushed U.S. yields significantly higher.

Yields rose as Wall Street gained on Thursday in anticipation of strong corporate earnings, and as geopolitical worries eased on U.S. President Donald Trump's suggestion that a military strike on Syria may not be imminent.

"The dollar had not shown a strong correlation with U.S. yields recently. But the correlation returned somewhat, with currencies taking notice of such a spike in yields," said Junichi Ishikawa, senior FX strategist at IG Securities in Tokyo.

"Risk aversion in equities will need to keep receding for the dollar to remain supported. There is no change to the equation of 'Trump risk' dictating market direction."

The common currency has risen 0.4 percent this week, supported by comments from European Central bank officials that reinforced expectations towards monetary policy normalization.