WASHINGTON - US President Donald Trump said on Monday he is seeking a "historic increase" in military spending to be funded by cuts elsewhere in government.

Trump will seek to boost Pentagon spending by $54 billion in his first budget proposal and slash the same amount from non-defense spending, including a large reduction in foreign aid, a White House budget official said.

"This budget will be a public safety and national security budget," Trump told state governors at the White House. "It will include an historic increase in defense spending to rebuild the depleted military of the United States of America at a time we most need it," he said.

The US military is already the world's most powerful fighting force and the United States spends far more than any other country on defense.

The Pentagon has finished plans to intensify the fight against the Islamic State group, officials said Monday, presenting Donald Trump with options to meet a key campaign pledge.

“The White House will begin reviewing the recommendations,” the official said on condition of anonymity. Trump had demanded that top brass find additional ways to defeat jihadists who still control a swath of northern Syria and Iraq and have inspired attacks on the West.

That review is now complete, and Defense Secretary Jim Mattis will present the findings to Trump’s top national security advisors later Monday.

Meanwhile, more than 120 retired US generals and admirals urged Congress on Monday to fully fund US diplomacy and foreign aid, the same government functions expected to be targeted for cuts in President Donald Trump’s first budget proposal.

A White House budget official said on Monday that Trump would seek to boost military spending by $54 billion and cut the same amount from non-defense spending, including a large reduction in foreign aid.

President Trump’s nominee for the Navy secretary, Philip Bilden, has withdrawn from consideration for the post to become the second Pentagon nominee to refuse a job under the Republican commander-in-chief.

Bilden’s Sunday decision was apparently because he knew he would have failed to untangle his financial investments in the vetting process, politico reported.

"Mr. Philip Bilden has informed me that he has come to the difficult decision to withdraw from consideration to be secretary of the Navy," US Defence Secretary James Mattis said in a statement.

Earlier this month, billionaire investment banker Vincent Viola also withdrew his nomination for the secretary of US Army, due to complications in regard to potential conflicts of interests during a review by the US Office of Government Ethics.

Moreover, the US claimed its seat Monday on the Human Rights Council under the new presidency of Donald Trump, whose election has provoked deep concern over the body's future.

Over its 11-year history, the council has come in for criticism, including allegations that it has, at times, been co-opted by rights abusers who push resolutions attacking their geopolitical rivals, with genuine rights issues marginalised.

But the 47-member panel has had successes - thanks to support from Barack Obama's administration which held a seat on the council for most of his eight-year term, civil society groups say.

Many of the issues prioritised by Obama's UN envoys - including violations in North Korea, Myanmar, Sri Lanka and South Sudan - remain on the agenda.

In a keynote address, United Nations Secretary General Antonio Guterres warned that the world was facing "a time of urgency" and that the council was needed more than ever.

"Disregard for human rights is a disease, and it is a disease that is spreading," he said.

"The Human Rights Council must be part of the cure."

Trump's State Department has not yet named an envoy to the body and was represented at Monday's session by veteran foreign service officer Erin Barclay.

Trump's international agenda remains murky but rights advocates have warned that the early signs do not bode well for either the council or the broader human rights agenda.

"Clearly 'America First' does not suggest an approach that (prioritises) multilateral engagement," said John Fisher of Human Rights Watch (HRW) in Geneva, referring to Trump's foreign policy doctrine.

HRW also reacted to media reports that the US was considering quitting the council - before its term expires in 2019 - over the body's treatment of Israel.

"A decision by the United States to withdraw from the UN Human Rights Council over its criticism of Israeli policy and its overall effectiveness would be a misguided and shortsighted step," the group's UN director Louis Charbonneau said in a statement.

Pro-Israel groups have repeatedly noted that the Jewish state has been targeted by more rights council resolutions than any other nation.

Palestinian president Mahmud Abbas, who addressed the opening session, said his people's issue would be a "litmus test" for the council's effectiveness.

Assuming the US keeps its seat, there is "significant concern" about Washington's capacity to take a leadership role based on Trump's early moves, according to Fisher.

"When the administration has issued an executive order that bans travel from seven mainly-Muslim countries it erodes the US' moral credibility and ability to engage in initiatives around the UN," Fisher told AFP.

Trump's travel ban has been blocked in court.

For UN rights chief Zeid Ra'ad Al Hussein, nations have a duty to resist "political actors ... (who) threaten the multilateral system or intend to withdraw from parts of it".

"Our rights, the rights of others, the very future of our planet cannot, must not be thrown aside by these reckless political profiteers," Zeid said in his opening speech.

The precursor to the rights council was the UN Commission on Human Rights, a body deemed so dysfunctional that former UN secretary general Kofi Annan scrapped it.

When the new council was born in 2006, the US administration of George W. Bush did not fight for a seat or meaningfully engage, according to a January report from the Council on Foreign Relations (CFR) think-tank.

The early years saw countries like Algeria, Pakistan and Saudi Arabia controlling the council, the CFR said, arguing that things began to turn when Obama's administration secured a seat in 2009.

The US began "to chip away at the council's deficiencies while strengthening its capacity as a credible international human rights institution," it said.

The think-tank noted that US influence on the council was decisive in setting up major probes in Burundi, North Korea, Syria and other hotspots.

Even if Trump's rights-related pronouncements have been "limited", he has "stressed the need for the United States to be seen as winning on the international stage", it said.

And engaging with the council could "advance these goals", it argued.