By Richard Cowan

WASHINGTON (Reuters) - The U.S. Congress and President Donald Trump neared agreement on Tuesday on legislation to battle the spreading coronavirus with as much as $9 billion, but a dispute over the cost of vaccines held up a deal, Senate Democratic Leader Chuck Schumer said.

Leaders in the House of Representatives and Senate hoped to resolve the dispute and approve the emergency legislation by the end of this week.

A source close to the negotiations, who asked not to be identified, said that two issues must first be resolved: Democrats insist that the spending bill contain language stating that any coronavirus vaccine be priced at a "fair and reasonable" level. Democrats also want the government to help pay for vaccines to help those who might not be able to afford them.

Republican aides were not immediately available for comment.

Trump said the measure would appropriate about $8.5 billion - far above the $2.5 billion he initially requested last month. And House Majority Leader Steny Hoyer, noting that the measure was still being written in Congress, said it could inject "$8 or $9 billion" into the U.S. economy.

Depending on when Republicans and Democrats settle their dispute, the bill could be debated by the full House on Wednesday or Thursday. Once passed by the House, the Senate is expected to attempt to act promptly.

The legislation is one part of a multipronged approach emerging from Washington following multiple deaths in Washington state this week from illnesses caused by the highly contagious coronavirus.

Earlier on Tuesday the Federal Reserve cut interest rates by a half percentage point to a target range of 1.00% to 1.25% in an attempt to cushion the economy against the impact of the virus, which could slow consumer spending and disrupt business activities.

U.S. health officials have been ramping up the government's ability to do more testing of patients suspected of having been infected by the new coronavirus, which was first detected in China late last year.

There also are efforts by pharmaceutical companies and Washington to speed the development of a vaccine for the coronavirus.

While details were still not available, the House's emergency spending could contain money to help state and local governments respond to local health emergencies and possibly provide interest-free loans for small businesses affected by an outbreak, Democratic lawmakers said.

On Wednesday, the top four leaders of the House and Senate are scheduled to be briefed by Capitol officials on responses to the coronavirus and the possible impact on day-to-day operations of Congress.

A senior House Democratic aide said there have been no discussions of limiting tourism in the Capitol complex or shutting public galleries for viewing House and Senate debates.

Last Friday, House lawmakers were advised to develop alternative work arrangements for aides if the virus becomes widespread.

(Reporting by Richard Cowan, David Morgan, Jeff Mason and Lisa Lambert; Editing by Chizu Nomiyama and Jonathan Oatis)