Trump, Obama row flares

President Donald Trump is asking Congress to probe "potentially politically motivated investigations" during the 2016 campaign, the White House said Sunday.

The announcement came one day after Trump took to Twitter to accuse his predecessor Barack Obama of tapping his phones ahead of the November election, without providing evidence of the explosive charge.

An Obama spokesman has denied Trump's accusation as "simply false."

In his statement, White House Press Secretary Sean Spicer referred to unspecified reports of "potentially politically motivated investigations immediately ahead of the 2016 election" as "very troubling."

"President Donald J Trump is requesting that as part of their investigation into Russian activity, the congressional intelligence committees exercise their oversight authority to determine whether executive branch investigative powers were abused in 2016," Spicer said.

He added that there would be no more comment on the matter from Trump or the White House.

Trump leveled his charges against Obama early Saturday, at the end of a week in which his administration was battered by controversy over communications between Russian officials and some of his senior aides including Attorney General Jeff Sessions.

"I'd bet a good lawyer could make a great case out of the fact that President Obama was tapping my phones in October, just prior to Election!" Trump wrote.

"How low has President Obama gone to tapp (sic) my phones during the very sacred election process. This is Nixon/Watergate. Bad (or sick) guy!" he wrote in another tweet, referring to the political scandal that toppled president Richard Nixon in 1974.

Meanwhile, US media reported that Trump is expected to sign a revised travel ban today, just over a month after his original decree sowed controversy across the United States and chaos at airports.

The president will sign the new executive order at the Department of Homeland Security, according to Politico, which cited senior government officials.

It was unclear what changes Trump planned to make, according to the publication.

Trump's original January 27 order was widely criticised as amounting to a ban on Muslims.  However, the order was halted after two judicial setbacks -- a nationwide freeze on Trump's ban by a US district judge in Seattle and a subsequent ruling by San Francisco's Ninth Circuit Court of Appeals upholding the suspension.

Meanwhile, the White House budget director confirmed Saturday that the Trump administration will propose "fairly dramatic reductions" in the US foreign aid budget later this month.

Reuters and other news outlets reported earlier this week that the administration plans to propose to Congress cuts in the budgets for the US State Department and Agency for International Development by about one third.

The United States spends just over $50 billion annually on the State Department and USAID, compared with $600 billion or more each year on the Pentagon.