Washington (CNN) President Donald Trump said Monday he is less inclined to make a deal with Iran as Tehran claimed to have arrested CIA operatives and US allies announced their own effort to secure shipping in the Persian Gulf, in a possible sign of division with Washington.

Speaking in the Oval Office, Trump deployed his characteristic tactic of mixed messaging, sounding downbeat about the prospects for diplomacy, despite earlier signals that he has been looking to speak with Iran's leaders.

"Frankly it's getting harder for me to want to make a deal with Iran," Trump said, citing the country's increasingly hostile rhetoric and combative behavior. "Right now, they're a very mixed up country," Trump said. "Their country's in turmoil."

Trump said he was satisfied to watch the situation unfold, adding that the US was prepared to respond to any scenario. "Whatever it is, it is," he said. "I'm just going to sit back and wait." Later, Trump added that "we are ready for the absolute worst and we're ready for sense, too. ... We are very geared up."

"Heavy heart'

Trump made his comments as the US and Iran continue to accuse each other of lying about tanker seizures, drone shootdowns and more, adding to the confusion surrounding escalating tensions in the Persian Gulf.

The President spoke shortly after Iran claimed that it had detained 17 citizens for spying for the CIA. Trump and other senior officials quickly declared the claims to be a lie, even as Tehran tried to bolster its case by releasing photos and footage they claimed was provided proof and said some members of the group would be put to death.

Hours earlier, the UK's top diplomat had announced that Britain would be ramping up its military presence in the Gulf and working with Europe to establish a joint maritime protection force to patrol it.

The announcement came days after Iran seized a British tanker in the Gulf, a move widely seen as retaliation for the UK impounding an Iranian tanker off the coast of Gibraltar. "It is with a heavy heart that we are announcing this increased military presence in the Gulf," Foreign Secretary Jeremy Hunt told the House of Commons on Monday.

"We do not seek confrontation with Iran. We have taken every available opportunity to reduce confrontation," Hunt emphasized. But he described Iran's seizure of the British tanker as a violation of international law and "an act of state piracy." The UK, he said, "must also react to the world around us as it is and not how we wish it to be."

The joint UK-European force Hunt announced parallels a similar effort the US has been trying to launch called Operation Sentinel, and could represent another example of division between Washington and its European allies over how to deal with Iran.

The US had been urging regional and international parties to take part in Operation Sentinel, which Washington casts as an effort to secure freedom of navigation in the Persian Gulf, the Strait of Hormuz and the Gulf of Oman, crucial waterways for the passage of global oil supplies.

The UK reportedly declined to participate in the US initiative. Asked Wednesday about the possibility that US economic pressure on Iran contributed to its seizure of the British tanker and what the US would to do help get it back, Secretary of State Michael Pompeo essentially said it was London's problem.

Differences with the US

"The responsibility in the first instance falls to the United Kingdom to take care of their ships," Pompeo said in an interview with Fox News. The State Department declined to elaborate on or explain the secretary's remark.

Pompeo went on to deny US pressure has played any role in Iran's actions in the Gulf. "This isn't because of American sanctions," he told Fox. "This is because of the theocracy, the leadership in Iran, their revolutionary zeal to conduct terror around the world for now four decades continues."

A UK official told CNN that France had agreed to work on the joint protection force, that the two are encouraging other allies to join and that they would be presenting this to an International Force Generation Conference to be held in Tampa, Florida, on Thursday, that will also feature a discussion on burden-sharing.

"We work closely with the US on Iran, as we do on a wide range of security issues, but we are very clear where our position on Iran with the US differs," the official said.

"Any new mission should have integrated US support, but must be focused on protecting shipping in the Gulf, not escalating tensions with Iran," the official said.

The official noted that the UK cooperates closely with the US on maritime security and plays a leading role in the US-led, 33-nation Combined Maritime Forces partnership that provides maritime security in the Gulf.

Former CIA Director Leon Panetta told CNN on Monday that the best chance the US has to pressure Iran lies in working closely with its allies. "Very frankly, that will increase our leverage," Panetta said.

With tensions simmering in the Gulf, Panetta said the President should follow up on his offer to talk to Iran without preconditions.

"The options are pretty clear at this point," Panetta said in an interview on CNN's "The Lead with Jake Tapper."

"The first is war with Iran and the United States and neither side, I think, wants that to happen. The second is we continue the current stalemate of each side poking the other ... trying to change them ... and that's not going to happen either."

Panetta said that neither side was going to accept the conditions the other was putting forward for talks.

'Only one alternative'

"There's only one alternative, whether they want to admit it or not," Panetta continued, "which is negotiations ... the President suggested negotiating without any preconditions. I think that's a pretty good approach Iran ought to consider."

Panetta said he also agreed with Trump's assessment of Iran's claims about the spy ring it claims to have busted. "I think the President is probably in the right place with that," Panetta said. "These countries, if they're going after spies, they don't usually announce that they're going after spies. To do it this way is part of the show. I suspect many of them have no relationship to spying."

Both the President and Pompeo said Iran was lying in its claims about having arrested CIA spies -- "totally false," Trump tweeted -- and in their denials that the US had downed an Iranian drone.

"There's a lot of proof on the ocean floor," Trump said Monday.