U.S. President Barack Obama said on Wednesday that he and British Prime Minister David Cameron agreed that there is still space and time for a diplomatic solution on Iran's nuclear issue, but he also warned of a " shrinking" window for diplomacy.

Speaking at a joint press conference with visiting British Prime Minister David Cameron at the White House, Obama said diplomacy is the best choice for the leadership in Iran, and urged Tehran to seize the opportunity of negotiations with world powers to avert "even worse consequences."

"In the past, there has been a tendency for Iran in these negotiations to delay, to stall, to do a lot of talking but not actually move the ball forward," he said, warning that the window for diplomacy on the nuclear issue is "shrinking."

Obama's remarks came after the P5+1 countries, namely the United States, China, Russia, France, Germany and Britain, agreed to resume negotiations with Iran over its disputed nuclear program, with the date and venue for the talks to be decided.

Cameron noted that the six countries are serious about the potential talks, and urged Iran to meet its international obligations.

"If it refuses to do so, then Britain and America, along with our international partners, will continue to increase the political and economic pressure to achieve a peaceful outcome to this crisis," he warned.

Israel has been clamoring for a preemptive strike on Iran's nuclear facilities before the country obtains the ability to make nuclear bombs. The Obama administration is trying to appeal to Israel for more time to allow sanctions to work.

The West has long been accusing Iran of trying to develop a nuclear weapon under the disguise of civilian programs, which has always been rejected by Tehran.