* Euro turns lower after Le Pen gains in Opinionway poll
* Dollar index rises, earlier hit 5-month lows
* Eyes on weekend G20 meeting
* Graphic: World FX rates in 2017 tmsnrt.rs/2egbfVh
By Ritvik Carvalho
LONDON, March 17 (Reuters) - The euro fell back against the dollar on Friday after a poll showed far-right anti-EU leader Marine Le Pen extending her lead over centrist Emmanuel Macron in the first round of France's presidential elections.
The Opinionway poll also showed Le Pen, who has pledged to take France out of the euro, narrowing Macron's lead in the second round run-off.
The euro traded broadly flat in morning European trade after two days of gains against the dollar before slipping to a day's low of $1.0732, down 0.3 percent, after the poll was published.
Separately, an Ipsos poll showed Macron gaining on Le Pen's first round lead.
"One of the things to remember for the euro dollar is its kind of overshot ... especially in terms of euro zone political risks this week," said ING currency strategist Viraj Patel.
"Anything like this, like these polls - potentially is a catalyst for triggering a correction in the euro."
The euro has been rising since European Central Bank President Mario Draghi last week said the bank saw less urgency in taking steps to prop up eurozone growth and inflation, encouraging speculation the bank was on the verge of reining in ultra-loose monetary policy that has undermined the currency.
Another ECB policymaker, Ewald Nowotny, told a newspaper on Thursday that the bank was still to decide whether raise interest rates - also a potential positive for the currency - before ending its bond purchase programme.
The euro move prodded the dollar into positive territory after it plumbed five-week lows against its peers in the wake of the Federal Reserve's cautious message this week on future interest rate hikes.
The dollar index, which measures the greenback against a basket of six major rivals, rose 0.2 percent to 100.40. It was still down almost 1 percent overall for the week and 1.2 percent since the Fed hiked rates on Wednesday.
The meeting of G20 financial leaders in Baden Baden starting later on Friday will be among the closest watched by the currency market for years.
Any hints of a broader push by Washington against an appreciating dollar are likely to weaken the currency.
But a softening of the joint draft statement's language on trade, removing a rejection of protectionism, speaks to a promised rise in U.S. tariff barriers which has so far largely been seen as dollar-positive.
German Finance Minister Wolfgang Schaeuble told Reuters in an interview published on Friday that the Trump administration's protectionist stance could complicate the talks and force policymakers to omit the disputed trade issue.
President Trump also meets with German Chancellor Angela Merkel on Friday at the White House.
"The primary driver (for the dollar from here) is going to be what's going to transpire at the G20 meeting more than anything else, where the U.S. will reiterate its stance that it's trying to make sure it gets fairer trade," said Valentin Marinov, head of FX strategy at Credit Agricole in London.
"Investors won't be completely embracing the idea of buying dollars just yet." (Editing by Hugh Lawson and Richard Lough)