* Obamacare replacement vote key test for Trump in Congress
* Sterling helped by retail sales numbers
* Aussie sinks on China worries; iron ore price fall (New throughout, updates prices and market activity to U.S. market open; new byline, changes dateline, previous LONDON)
By Saqib Iqbal Ahmed
NEW YORK, March 23 (Reuters) - The dollar hovered near a four-month low against the Japanese yen on Thursday ahead of a vote on Republican healthcare plans seen as a litmus test of U.S. President Donald Trump's ability to legislate in Congress and deliver on tax and spending promises.
Trump was set to make a final push in the House of Representatives to secure the votes to begin dismantling Obamacare, with signs that enough Republicans might defect to jeopardize one of his top legislative priorities.
"Today, more than anything, the U.S. House vote is what people are looking at," said Alvise Marino, FX strategist at Credit Suisse in New York.
"If the (proposal) does not pass," he said, "that suggests the government's ability to actually introduce meaningful changes and meaningful policies is probably going to be considered lower."
The dollar was roughly steady at 111 yen, after dipping to a low of 110.64 yen earlier in the session.
The greenback soared to a 14-year peak after Trump's election last year on expectations of tax changes that would lead to billions repatriated to the United States and allow the White House to spend more, boosting growth, inflation and interest rates.
That faith has evaporated steadily since the turn of the year, and the dollar has fallen against all of its major peers in response.
If the House does not approve the healthcare proposal, "it would be dollar-negative and somewhat negative also for general risk appetite," Marino said.
The dollar traded in a tight range. The dollar index, which measures the greenback against a basket of six major currencies, was little changed at 99.702.
"Until we get a concrete signal on fiscal policy, currency markets remain in a holding pattern," said currency strategist Erik Nelson of Wells Fargo in New York.
Sterling jumped to a nearly one-month high against the dollar after UK retail sales data came in much higher than expected, soothing worries about weakening consumer sentiment in Britain as it prepares to leave the European Union.
The numbers bolstered speculation that the Bank of England might be able to raise interest rates at least once in the next year, driving the pound half a cent higher.
Australia's dollar, fell 0.66 percent to a 1-week low against the greenback on a slump in prices for its iron ore exports and nervousness in China's money market.
Reporting by Saqib Iqbal Ahmed; Editing by Lisa Von Ahn