The US Federal Reserve has opened the door further for an interest rate hike as early as June, ending its pledge to be "patient" in normalising monetary policy. 

However, markets bet on a September hike after it downgraded the expected pace of growth and inflation.              

Stock markets rallied after the Fed statement, while the US 10-year Treasury yield dipped below 2% for the first time since 2 March.

The euro rose against the dollar on forecasts that appeared to argue against a June move.            

But the Fed signalled a more cautious outlook for US economic growth and slashed its projected interest rate path in a sign that it remains concerned about the health of the recovery.             

In its statement following a two-day meeting, the US central bank’s policy-setting committee repeated its view that job market conditions had improved and gave its strongest signal to date that it was nearing its first rate hike since 2006.

Fed chief Janet Yellen has kept rates at near zero since taking over as head of the central bank in February 2014. 

But the statement put a June rate increase on the table, though it also allowed the Fed enough flexibility to move later in the year, stressing that any decision would depend on incoming data.         

"The committee anticipates that it will be appropriate to raise the target range for the federal funds rate when it has seen further improvement in the labour market and is reasonably confident that inflation will move back to its 2% objective over the medium-term," the Fed said in its statement.             

It said a rate increase remained "unlikely" at its April meeting and its change in rate guidance did not mean the central bank has decided on the timing of a rate hike.             

It had previously said it would be patient in considering when to bring monetary policy back to normal.             

While the Fed showed that it's nearing a hike, fresh forecasts from the central bank revealed a more cautious view of the economic outlook.

The Fed's quarterly summary of economic projections cut its inflation outlook for 2015 and dramatically lowered its projected interest rate path, data known as the Fed's "dot plots".             

The Fed continued to acknowledge that inflation was running below expectations, weighed down in part by falling energy prices.             

"Inflation has declined further below the committee's longer-run objective," the Fed said.             

While Ms Yellen lays the ground for the rate 'lift-off', the Fed continues to grapple with muddy economic data: strong job creation, continued growth, and healthy consumer demand in the United States, but a global collapse in oil prices and a rapid run-up in the dollar that could mean it remains far from its 2% inflation target.

The Fed downgraded its view of economic activity, saying growth has "moderated somewhat", a departure from December when it cited economic activity expanding at a solid pace.             

The federal funds rate has been at its low point since December 2008. The last time the Fed raised rates was in June 2006, when a roaring housing market and strong economic growth prompted it to push its target rate to 5.25%.             

Investors and economists are split over whether the initial hike will come in June or in September.

Trading in federal funds futures contracts points to a September hike, while a recent Reuters poll of 70 economists indicated an even split between June and later in the year.             

There were no dissents on the Fed statement.