(Adds Trump, analyst, King comments, background)
WASHINGTON, Aug 28 (Reuters) - U.S. lawmakers are expected to pass a large aid package for victims of Hurricane Harvey, but specifics of the plan and its price tag are unclear as Congress awaits a funding request from the Trump administration.
Rain continued to pound Houston and the Gulf Coast on Monday as President Donald Trump said he expected rapid federal action to help fund a costly recovery. He plans to visit Texas on Tuesday to see storm-hit areas.
"We're dealing with Congress. As you know it's going to be a very expensive situation," he told reporters in the White House.
Historic flooding from Harvey, which came ashore in Texas last week as a powerful Category 4 hurricane and is now a tropical storm, has killed at least seven people in Texas and was expected to drive 30,000 from their homes.
Wall Street analysts estimated insured losses of up to $20 billion, making Harvey one of the costliest storms in history for U.S. insurers.
After past disasters, Congress approved billions of dollars in funds to help with relief and recovery, but in recent years, fiscal conservatives have raised questions about costs.
Congress will return next week from summer vacation, with the hurricane complicating an already difficult fiscal situation with the federal budget and Trump's Mexican border wall proposal.
Current government funding runs out on Sept. 30. Congress must approve a measure to keep the government funded and prevent a shutdown. Trump threatened last week to shut down the government if Congress did not agree to $1.6 billion in funding to start building his proposed wall on the U.S.-Mexico border.
Harvey "will increase the pressure on Washington to not shut down the government, but it also makes the September 30 package more cumbersome and complicated," Chris Krueger, policy analyst at financial firm Cowen & Co, said in a research note.
Asked if Harvey made him reconsider his shutdown threat, Trump said: It has nothing to do with it, really. I think this is separate. This is going to go really very, very quickly."
Congressional Republicans have not spelled out their plan for dealing with the budget and a related, must-pass increase in the federal debt ceiling. Some aides and analysts have speculated that those issues might be swept into a single piece of legislation, possibly including Harvey aid.
House of Representatives Democratic leader Nancy Pelosi said on Monday that "Republicans must be ready to join Democrats in passing a timely relief bill."
Federal Emergency Management Agency Administrator Brock Long said more than 450,000 people were expected to seek disaster assistance because of catastrophic flooding.
"We will help those affected by this terrible disaster. The first step in that process is a formal request for resources from the administration," said AshLee Strong, spokeswoman for House Speaker Paul Ryan.
'HAVE TO DEAL WITH THIS APPROPRIATELY'
A Senate Republican aide said it was too soon to say what was needed. "The committee is monitoring the situation in Texas closely," said Chris Gallegos, a spokesman for the Republican majority on the Senate Appropriations Committee.
There is only about $3.3 billion in the federal disaster relief fund. Congress approved $62.3 billion in aid after Hurricane Katrina devastated Gulf Coast communities and flooded New Orleans in 2005.
Texas Republican Representative Pete Sessions told MSNBC he expected lawmakers to back any aid package as long as it was not bloated beyond the needed storm response.
Some conservatives have balked in the past at authorizing money for disaster relief. In 2005, then-Indiana Republican Representative Mike Pence, now vice president, called on the floor of the House for "offsetting" money spent on Katrina relief with cutbacks elsewhere.
Almost the entire Texas delegation - including Sessions and Republican Senator Ted Cruz - opposed the $50.5 billion aid package that Congress approved three months after Hurricane Sandy hit New Jersey and New York in 2012. Opponents argued that the Sandy package funded things unrelated to the disaster.
"The Sandy relief bill had more pork in it than a bacon factory," said Representative Blake Farenthold, a Republican who represents Corpus Christi, which was hit hard by Harvey.
Republican Representative Pete King of New York said in a Twitter message on Monday: "I won't abandon Texas the way Ted Cruz did New York."
(Additional reporting by David Morgan; Editing by Kevin Drawbaugh and Peter Cooney)