By winning full control of Congress, the Republicans have the chance to pile political pressure on President Barack Obama over national security issues and possibly push through an increase in military spending at the expense of social programs.

The following is a look at how Tuesday's election result could affect national security policy:

- US intelligence agencies -

A Republican-controlled Senate likely will mean less friction between lawmakers and America's spy services, after prominent Democrats on the Senate Intelligence Committee clashed repeatedly with spy chiefs over electronic surveillance, CIA drone strikes and divulging past abuses.

The outgoing Democratic chair of the Senate Intelligence Committee, Dianne Feinstein, was at loggerheads with CIA Director John Brennan over a long-delayed report on the agency's interrogation methods over the past decade -- including waterboarding and other abuses.

Feinstein and other Democrats demanded a full account of the excesses to be made public, while the Central Intelligence Agency has insisted on censoring parts of the report.

A Republican senator tipped to replace Feinstein as chair of the committee, Richard Burr, is known for his reserved manner and his unflinching support for the intelligence agencies and their sweeping surveillance powers.

Analysts say Burr would be inclined to ease off on the spy services, and would have little time for concerns raised by civil liberties groups.

Public hearings for the committee might also become a rare event if Burr takes charge.

"If I had my way, with the exception of nominees, there would never be a public intelligence hearing," Burr was quoted as saying earlier this year.

The committee's make-up will shift, as Democrat Mark Udall -- a strong advocate of reforming electronic spying and dogged oversight -- lost his Senate seat in Colorado on Tuesday.

- The war against the IS group -

With the outspoken and hawkish John McCain expected to take over as chairman of the Senate Armed Services Committee, the Obama administration will be facing a hostile reception at hearings on the air war against Islamic State jihadists and other issues.

McCain and some fellow Republicans have called the current campaign in Iraq and Syria "half-hearted" and demanded the administration take bolder action, including expanding air strikes, confronting the Syrian regime and sending more US troops to aid Iraqi forces.

On Afghanistan, the Republicans will accuse Obama of withdrawing troops too quickly.

Although McCain will have a high-profile platform to create headaches for the Obama administration, on most policy issues, the Republicans' objections will be mainly symbolic. Their leverage rests with budgets and confirming nominees for senior posts.

- US defense spending -

While Obama's team is braced for difficult congressional hearings, the real challenge will come when lawmakers take up the budget.

Until now, Obama and his fellow Democrats were able to tie military spending to other domestic spending, so that any cut to social programs had to be accompanied by equivalent cuts to defense funding.

But that could end with the new Republican majority in the Senate.

The Republicans could decide to end automatic budget reductions and back a defense-only budget "and then Obama will be placed in a difficult position," said one administration official on condition of anonymity.

Obama might be forced to veto a defense funding bill, and allow Republican opponents to paint him and the Democrats as failing to "support the troops."

If Obama chooses not to use his veto power, the end result could mean ramped up defense spending, which already is running at about $600 billion a year.

The defense industry stands to gain if that's the case.

Weapons firms contributed a record amount to candidates in this year's midterm election, with more than $27 million in campaign donations.