NEW YORK/WASHINGTON (Reuters) - President Donald Trump sought on Monday to bring the nation’s largest insurance companies on board with his plans to overhaul Obamacare, saying their help was needed to deliver a smooth transition to the Republicans’ new plan. “We must work together to save Americans from Obamacare – you people know that and everyone knows that - to create more competition and to bring down prices substantially,” Trump told insurers at a meeting at the White House. The gathering took place a day before Trump was to deliver a major policy speech to the U.S. Congress. In attendance at the meeting were insurers who participate in the Obamacare health insurance exchanges as well as some that have pulled most or all of their Obamacare individual insurance offerings. The president needs insurers to participate in the individual insurance market to keep up competition and keep costs in check. The speech to Congress is a chance for Trump to elaborate on his healthcare policy, one of his top domestic priorities. Trump and Republicans have vowed to repeal and replace the Affordable Care Act, former President Barack Obama’s signature piece of domestic policy, but have not released details yet. Trump told the insurers that his changes would include expanded healthcare savings accounts, which are tax-free savings accounts typically used with high-deductible insurance plans, and the sale of health plans across state lines. He also said that he wanted states to have more flexibility but did not provide details. Trump previously discussed these ideas on the campaign trail. It is unclear how they would be implemented, or what changes he might make to Medicaid expansion, another key component of the Obamacare law. Trump told insurers, including UnitedHealth Group Inc, Anthem Inc and Aetna Inc, that he was directing Health and Human Services Secretary Tom Price to work with them “to ensure a smooth transition to the new plan.” The administration recently granted the insurers one of their biggest requests and proposed a rule that would tighten eligibility verification for subsidized plans and allow them to seek unpaid premiums. Trump is also seeking support from the nation’s governors for changes. The Obamacare law, which extended health insurance to 20 million Americans, has been popular in many states, even those controlled by Republicans. But it has also been criticized for its steep premium increases. At a meeting with Trump and governors on Sunday, Price said he expected to have a new healthcare plan in three to four weeks, to which Trump responded he hoped to see a plan in two weeks, said Virginia Governor Terry McAuliffe.  Nevada Governor Brian Sandoval said many conversations during this weekend’s meeting of the National Governors Association centered on Medicaid, the massive government health insurance program for the poor, and how to ensure those who received coverage under the Medicaid expansion could maintain coverage. Trump said on Monday that he wanted to win support from Democrats for the plan. McAuliffe, a Democrat, said it would be “disastrous” for Republicans to repeal Obamacare without a proper replacement. “The political rhetoric of the campaign has hit the reality of governing,” he said.  