Donald Trump's chief strategist Steve Bannon has appealed to conservatives to unite behind the Republican president as he presses his agenda.

Bannon took to the stage along with White House chief of staff Reince Priebus at the four-day Conservative Political Action Conference, telling the gathering, "We want you to have our back" in upcoming battles, and denouncing media criticism of Trump.

The early days of the administration have been marked by deep post-election divisions between Trump backers and liberals over the new president's travel ban on refugees and people from seven Muslim-majority countries, as well as moves to increase deportations of illegal immigrants and to build a wall on the border with Mexico.

While conservatives are celebrating Trump's role in delivering them a victory in November's election, his agenda veers from traditional right-wing principles like limited government and open trade.

Republicans who control the White House and Congress also are arguing over how to dismantle and replace President Barack Obama's landmark healthcare law.

Bannon and Priebus both sought to dispel a sense of disorder in the White House portrayed in media accounts.

Referring to media criticism of Trump and echoing the president's attacks on the media, Bannon warned, "It's going to get worse every day" as Trump presses forward with his 2016 campaign promises.

"If you think they're going to give you your country back without a fight you are sadly mistaken," said Bannon, who formerly ran the confrontational right- wing website Breitbart News. He blamed the "corporatist, globalist media that are adamantly opposed to an economic nationalist agenda" under Trump.

The CPAC conference, once a fringe event but is now decidedly in the Republican mainstream, is being held in suburban Maryland, attended by an estimated 10,000 activists.

White House adviser Kellyanne Conway credited Trump with revitalising the Republican Party's right wing.

"Every great movement ends up being a little bit sclerotic and dusty after a time, and I think they (conservatives) need an infusion of energy," Conway said.

Referring to Trump's expected attendance at the conference on Friday, she said, "I think by tomorrow this will be TPAC, this year. No doubt."