Washington, Jan 19 (IANS): US President Donald Trump has appeared to undercut his party's attempts to reach a budget deal with Democrats, on the eve of a possible government shutdown.

In a tweet, the Republican president criticised a sweetener added to the spending bill by congressional leaders to win Democratic lawmakers' votes, BBC reported on Thursday.

The White House later had to issue a statement maintaining the president fully endorsed the short-term measure.

The last US shutdown occurred in 2013 and lasted for 16 days.

The House of Representatives is due to vote on the spending measure on Thursday afternoon.

But it is unclear if there are enough votes to pass it in either the House or Senate.

At least some Democratic votes are needed to pass the budget measure ahead of the Friday midnight deadline.

Republican leaders also face resistance from their rank-and-file conservatives, who are demanding more military spending, among other things.

This so-called stopgap spending measure would keep federal agencies funded only until February 16.

The US government is already operating on its third temporary funding extension since this fiscal year began last October.

Democrats are demanding help for "Dreamers", more than 700,000 immigrants who entered the US illegally as children.

Liberals were in uproar when Trump last year ordered the Obama-era Deferred Action for Childhood Arrivals (Daca) programme, which shielded Dreamers from deportation, to end this March.

In order to convince Democratic lawmakers to back their budget bill, Republicans are offering a six-year extension of the Children's Health Insurance Program (Chip), which benefits lower-income families.

However, Democratic House leader Nancy Pelosi said on Thursday: "This is like giving you a bowl of doggy doo, put a cherry on top, and call it a chocolate sundae."

The president caused a minor muddle on Thursday morning when he tweeted: "CHIP should be part of a long term solution, not a 30 Day, or short term, extension!"

The President's posting appeared to contradict Republican lawmakers' legislative strategy.

A White House spokesman was forced to issue a clarification later clarifying that Trump did actually support the House measure.

Arriving at the Pentagon for a visit, the president told reporters the government "could very well" shut down.

Another conservative lawmaker vented his frustration with Trump.

"We don't have a reliable partner at the White House to negotiate with," said Senator Lindsey Graham, of South Carolina, according to the Washington Post.