By Patricia Zengerle

WASHINGTON, May 22 (Reuters) - U.S. President Donald Trump's administration plans to use a loophole and rising tensions with Iran to sell bombs to Saudi Arabia, even though Congress blocked such sales for months over concerns about civilian deaths in the war in Yemen, Senator Chris Murphy said on Wednesday.

"I am hearing that Trump may use an obscure loophole in the Arms Control Act and notice a major new sale of bombs to Saudi Arabia (the ones they drop in Yemen) in a way that would prevent Congress from objecting. Could happen this week," Murphy warned on Twitter.

Congressional aides said there are provisions of the Arms Control Act, which sets rules for international arms transactions, that would allow a president to approve a sale without congressional review in case of a national emergency.

In this case, they said Trump would cite rising tensions with Iran as a reason to provide more military equipment to Saudi Arabia, which he sees as an important U.S. partner in the region. Trump has touted arms sales to the Saudis as a way to generate U.S. jobs.

Trump previously declared an influx of immigrants a national emergency to bypass Congress and get $6 billion to build his wall along the Mexican border. Both Democrats and his fellow Republicans voted to block the move, forcing Trump to issue the first veto of his presidency.

It was not immediately clear what equipment would be sold to Saudi Arabia or when any sale might go ahead.

However, any such plan would run into resistance in Congress, from Trump's fellow Republicans as well as Democrats like Murphy, even in the Senate, where Republicans have a slim majority.

A handful of Republicans recently voted with Democrats in a failed effort to override Trump's veto of a resolution that would have ended U.S. support for the Saudi-led military coalition in Yemen's devastating civil war.

Many lawmakers from both parties have also expressed anger over the murder of journalist Jamal Khashoggi at a Saudi consulate in Turkey.

Senator Lindsey Graham, one of Trump's closest congressional allies, told CNN he would oppose the administration if it decided to go around Congress, citing Khashoggi's killing.

"We are not going to have business as usual until that issue is dealt with," Graham said.

The State Department declined comment. The White House did not respond to a request for comment.

The top Republicans and Democrats on the Senate Foreign Relations and House of Representatives Foreign Affairs committees, who review major international weapons deals, have been approving sales of defensive military equipment to Saudi Arabia.