* No GM, Delphi witnesses ruled out -Chairman Upton
* Sen. McCaskill says heavy focus on NHTSA too
* Two senators offer bill to force more industry reporting
* Reuters/Ipsos poll: 67 pct want tougher U.S. auto regulation (Recasts with Upton, McCaskill comments on possible additional witnesses, adds poll results)
WASHINGTON, March 25 (Reuters) - U.S. lawmakers are considering calling on former General Motors Co executives and employees from parts supplier Delphi Automotive to testify as they cast a wide net in their probe of GM's recall of 1.6 million vehicles with potentially lethal ignition-switch problems.
"We're not ruling anything out," House Energy and Commerce Committee Chairman Fred Upton told Reuters when asked if his committee would elicit testimony from former GM officials, including ex-CEOs, and Delphi officials who may have been directly involved in reviewing the problem that first arose in 2001.
On April 1, the current head of GM, CEO Mary Barra, is scheduled to testify at the maiden congressional hearing on the automaker's troubled cars, which have been linked to 12 deaths.
The 1.6 million recalled cars include 2005-07 Chevrolet Cobalts and Pontiac G5s, 2003-07 Saturn Ions and other models.
National Highway Traffic Safety Administration Acting Administrator David Friedman is also expected to be at the House hearing.
The hearings come as a new Reuters/Ipsos poll shows Americans want tougher federal regulation of the automobile industry.
The poll, conducted March 21-25, found that 67 percent of those surveyed said they either strongly agreed or somewhat agreed that the federal government needed to strengthen auto safety regulation.
GM and NHTSA were up against a Tuesday deadline for providing Upton's committee with a raft of information on how it responded, or failed to respond, to warnings that the ignition switches could unexpectedly turn off vehicle engines and safety equipment while the cars were operating.
"We'll see where Tuesday's (April 1) hearing takes us" before deciding next steps, Upton said.
Senator Claire McCaskill, who chairs a Commerce subcommittee that also intends to hold GM hearings in early April, told Reuters that "anything is possible" in regard to witnesses who could be called to testify, including former GM officials.
Besides the congressional investigation, the U.S. Department of Justice is conducting a criminal probe of GM officials, which could complicate the ability of some to testify before Congress.
FOCUS NOT JUST ON GM
McCaskill made it clear that federal regulators will be closely grilled in upcoming hearings.
"One of my biggest focuses is on NHTSA," McCaskill said.
"What did they know, when did they know it, why didn't they know more?" she added.
How deeply Congress probes GM and NHTSA could depend in part on the interest level of the American public, according to consumer safety advocates.
The Reuters/Ipsos poll found that auto recalls register on consumers' radar screens and that many remember safety problems that are a few years old.
Forty-six percent said they knew about a major vehicle recall by GM, while 38 percent were aware of one by Toyota, which suffered sudden, unintended acceleration problems that were the subject of congressional hearings in 2010.
The poll, with a sample of 1,175 Americans aged 18 and older, found that 29 percent said they were less likely to buy a GM car, with 75 percent of that group citing safety concerns.
Amid the growing scrutiny by Congress of GM, two senators on Tuesday offered legislation aimed at improving the auto industry's reporting of safety problems.
Democratic senators Edward Markey of Massachusetts and Richard Blumenthal of Connecticut introduced a bill that would require automobile manufacturers to provide more information about fatal accidents involving their vehicles and better public access to those reports.
Markey said a legislative fix was necessary after "a massive information breakdown at NHTSA has led to deadly vehicle breakdowns on our roads."
In 2000, Congress passed a law requiring an early warning reporting system for NHTSA to catch safety defects.
The two senators want to beef up that law by requiring automakers and auto equipment manufacturers to automatically submit accident reports and other documents that alert them to fatalities involving their equipment.
The information would have to be publicly released, unless it is exempted from the Freedom of Information Act.
Currently, the industry documents are provided to NHTSA if the federal agency requests them and are not automatically made public unless requested under FOIA, the senators said.
"Timely information can save lives when it reveals lethal defects," Blumenthal said. (Editing by Stephen Powell and Matthew Lewis)