By Andrew Marr BBC News political editor

The US must accept the importance of issues like a peace process for the Middle East, global warming and world poverty alongside terrorism and weapons of mass destruction, the prime minister will say on Tuesday.

In a speech to British ambassadors in London, Tony Blair will respond to domestic critics over Iraq by insisting that "it is massively in our national interest to remain the closest ally of the United States".

But he will add: "We should use that alliance to influence them to continue to broaden their agenda."

Mr Blair has been facing private criticism from senior colleagues who are worried that Britain might back the US in an attack on Iraq without clear new evidence or a fresh mandate from the UN - something the prime minister has been warned would contravene international law.

More generally, he faces the charge of simply doing whatever Washington wants.

'Real issues'

In his speech Mr Blair again attacks anti-Americanism, but tacitly acknowledges the criticism.

I would not commit British troops to a war I thought was wrong or unnecessary Tony Blair

He will say: "The problem that people have with the US is not that they don't believe that the weapons of mass destruction and terrorism are not real issues, but that they want to know that the US accepts that other issues, such as the Middle East, world poverty and global warming are real issues as well."

He cites the decision to go through the UN over Iraq as highly significant.

But it is no good, he argues, to attack the US for going it alone if, when Washington asks for help, everyone shuffles to the back of the queue.

"I would not commit British troops to a war I thought was wrong or unnecessary but the price of influence is that you do not leave the US to face the most difficult issues alone," he will say.

'Appalling poverty'

Unless action is taken against rogue states, including countries like North Korea, "it is only a matter of time before terrorists get their hands on WMD."

Tony Blair will say Britain and the US must remain close allies

A regime which refuses to disarm despite warnings from the United Nations, "threatens us... Unless the world takes a stand on this issue of WMD we will rue the consequences of our weakness."

But alongside that hard-line message, Mr Blair emphasises that in an interdependent world there can be no long-term stability unless the rich countries tackle "the appalling poverty that afflicts a third of the world's population" and emphasises the importance of reaching out.

He will emphasise also that Britain can be "a unifier" - strong in Europe and therefore influential with Washington, and will repeat his general support for the euro, though not going further than he usually does.