Washington - President Donald Trump heads into one of his most challenging weeks, juggling a renewed health care push and a looming budget deadline, and readying for a potential showdown with Democrats over paying for a border wall.The symbolic 100-day mark for the administration is on Saturday - the same day government could shut down without a budget deal. Trump has announced a rally in Pennsylvania that day.Aides stressed on Sunday talk shows that funding a wall along the US-Mexican border and a vote on an effort to repeal and replace ex-president Barack Obama's health care law were priorities. But they also expressed optimism that a shutdown could be avoided."I don't think anyone foresees or expects or would want a shutdown," said budget director Mick Mulvaney on Fox News Sunday.Trump would like to revive a failed effort by House Republicans to replace the Affordable Care Act, or "Obamacare". He also hopes to use a $1 trillion catchall spending bill to salvage victories on his promised US-Mexico border wall, a multibillion-dollar down payment on a Pentagon buildup, and perhaps a crackdown on cities that refuse to co-operate with immigration enforcement by federal authorities.But so far, negotiations have proven difficult, with disputes over the border wall and health law subsidies to help low-income people afford health insurance. House members received little information from leaders on a conference call on Saturday. A one- or two-week extension might be needed to prevent a shutdown.White House chief of staff Reince Priebus said on NBC's Meet the Press that he believes the spending bill will include "something satisfactory" to reflect Trump's desire to build a wall. The legislation would keep the government running through September 30, the end of the budget year.Priorities"We expect the priorities of the president to be reflected," Priebus said, citing ongoing talks with the House and the Senate. He added that "it'll be enough ... to move forward either with construction or the planning, enough for us to move forward through the end of September, to get going on the border wall and border security".House Democratic leader Nancy Pelosi of California described a border wall as "immoral" and "expensive" when asked if there was any scenario in which Democrats will agree to money for a wall to avoid a shutdown."Democrats do not support the wall," she said, speaking also on NBC. "Republicans on the border states do not support the wall."The Republicans have the votes in the House and the Senate and the White House to keep government open. The burden to keep it open is on the Republicans," Pelosi said. She noted that when Trump promised to build a wall during his campaign, he never indicated he would "pass billions of dollars of cost of the wall onto the taxpayer".On Obama's health law, Priebus said he'd like to have a vote on the GOP replacement bill in the House this coming week. But he insisted it didn't make too much difference to the White House whether the vote came next "Friday or Saturday or Monday"."It's a marathon, not a sprint," he said.TaxTrump tweeted a warning at Democrats on Sunday, saying: "ObamaCare is in serious trouble. The Dems need big money to keep it going - otherwise it dies far sooner than anyone would have thought."Trump is also planning to outline a tax cut plan on Wednesday. He told The Associated Press on Friday that it would include a "massive" tax cut for both individuals and corporations.On Fox, Mulvaney said to expect "some specific governing principles, some guidance, also some indication on what the rates are going to be." He added: "I don't think anybody expects us to roll out bill language on Wednesday."Speaking to the AP, Trump dismissed 100-day markers as "artificial". Still, his White House is eager to tout progress on the litany of agenda items he promised to fulfil in his first 100 days, despite setbacks including court bans on his proposed immigration limits and the high-profile failure in repealing and replacing Obama's health law.The president said on Friday he spent his first 100 days laying the "foundation" for progress later in his administration, including by building relationships with foreign leaders.